Lovelace

Termbank
1. A
1. Absolute Path
2. Ajonaikainen
konseptit
3. Alustaminen
muuttujat arvot
4. Argumentti
funktiot arvot
5. Arvo
arvot
6. Assignment
muuttujat arvot
7. Assignment Operator
muuttujat arvot operaattorit
8. Attribute
objektit
9. Attribuutti
Attribute
10. Avainsana
nimet
11. Ajaminen
Execution
12. Aliohjelma
Function
2. B
1. Boolean
ohjausrakenteet tyypit
2. Boolean Operator
ohjausrakenteet
3. Boolen operaattori
Boolean Operator
4. Branch
ehtorakenteet try-rakenteet
5. Bug
ongelmanratkaisu
6. Bugi
Bug
7. Builtin Function
funktiot
8. break
avainsanat toistorakenteet
3. C
1. Callback
funktiot
2. Carriage Return
merkkijonot tiedostot pakeneminen windows
3. Code Block
funktiot ohjausrakenteet
4. Code File
konseptit
5. Command Line Argument
terminaali
6. Comparison Operator
operaattorit ohjausrakenteet
7. Comparison Value
8. Condition
ohjausrakenteet
9. Conditional Statement
ohjausrakenteet
10. Conditional Structure
11. Constant
muuttujat arvot
12. Control Structure
ehtorakenteet toistorakenteet try-rakenteet
13. Ctrl + C
Näppäimistökeskeytys
14. Callback
Takaisinkutsu
15. continue
avainsanat toistorakenteet
4. D
1. Data
2. Data Format
tiedostot merkkijonot
3. Data Structure
konseptit listat sanakirjat
4. Debugging
5. Default Value
funktiot arvot parametrit
6. Dictionary
tietorakenteet
7. Docstring
dokumentointi
5. E
1. Epätosi
arvot
2. Error Message
ongelmanratkaisu
3. Escape
merkkijonot
4. Evaluointi
arvot lausekkeet
5. Event
konseptit
6. Exception
poikkeukset ohjaurakenteet
7. Execution
konseptit lausekkeet
8. Elementti
Item
9. enumerate
toistorakenteet listat
6. F
1. False
Epätosi
2. File Extension
tiedostot
3. File Handle
tiedostot objektit
4. Filename
tiedostot merkkijonot
5. Float
arvot tyypit
6. Format
merkkijonot tulostus
7. Function
funktiot
8. Function Call
funktiot lauseet
9. Function Definition
10. for
7. G
1. Generator
objektit toistorakenteet
2. Globaali muuttuja
muuttujat arvot
3. Global Scope
8. H
1. Handler
funktiot konseptit
2. Hyppy
ohjausrakenteet
3. Hardkoodaus
Kovakoodaus
9. I
1. if-lause
Conditional Statement
2. if-rakenne
Conditional Structure
3. Identifier
muuttujat funktiot
4. Indentation
konseptit
5. Index
listat arvot
6. Index Subscription
listat arvot
7. Infinite Loop
toistorakenteet
8. Input
konseptit merkkijonot
9. Interface
konseptit funktiot moduulit
10. Item
listat arvot
11. Iteration
toistorakenteet
12. import
moduulit
10. J
1. Jäsenfunktio
Method
11. K
1. Koodilohko
Code Block
2. Kahva
File Handle
3. Kutsu
Function Call
4. Key
arvot sanakirjat
5. Keyword Argument
funktiot
6. Kirjasto
moduulit
7. Kommentti
dokumentointi virheenetsintä
8. Kovakoodaus
arvot
9. Käyttöliittymäelementti
10. KeyboardInterrupt
Näppäimistökeskeytys
11. Koodi
Source Code
12. Komentorivi
Terminal
13. Komentokehote
Terminal
12. L
1. Lause
konseptit
2. Lauseke
konseptit
3. List
4. Literal
arvot
5. Local Variable
6. Loop
ohjausrakenteet
7. Loop Variable
toistorakenteet muuttujat
13. M
1. Muotoilu
Format
2. Main Program
konseptit
3. Merkki
4. Merkkijono
arvot tyypit
5. Method
objektit funktiot
6. Method Call
lausekkeet objektit
7. Module
8. Mutable
konseptit listat arvot
9. Muuntumaton
konseptit merkkijonot arvot
10. Määrittely
konseptit
14. N
1. Name Conflict
2. Namespace
konseptit funktiot moduulit
3. Newline
merkkijonot tiedostot
4. Nimeämätön vakio
vakiot arvot
5. Näppäimistökeskeytys
poikkeukset
15. O
1. Objekti
konseptit
2. Olio
Objekti
3. Ohjelmointityyli
4. Ominaisuus
objektit
5. Opening Mode
tiedostot
6. Operand
7. Operation
lausekkeet
8. Operator
9. Optional Argument
funktiot arvot parametrit
16. P
1. Paikanpidin
merkkijonot tulostus
2. Parameter
funktiot
3. Parametrization
4. Path
5. Poikkeus
ongelmanratkaisu try-rakenteet
6. Poikkeusten käsittely
ohjausrakenteet poikkeukset
7. Precedence
8. Printing
konseptit merkkijonot
9. Programming Problem
ongelmanratkaisu
10. Python Console
työkalut
11. Python Interpreter
työkalut
12. Presedenssi
Sidontajärjestys
17. R
1. Recursion
funktiot konseptit
2. Referring
muuttujat arvot objektit
3. Relative Path
4. Return
funktiot arvot
5. Return Value
18. S
1. Silmukka
Loop
2. Sapluuna
merkkijonot konseptit
3. Scope
lohkot konseptit
4. Separator
merkkijonot listat tiedostot syöte
5. Sequence
tietorakenteet toistorakenteet konseptit
6. Sidontajärjestys
konseptit lausekkeet
7. Suoritusjärjestys
Sidontajärjestys
8. Slicing
listat
9. Solution Model
ongelmanratkaisu
10. Source Code
konseptit
11. State
konseptit
12. Stub
funktiot ongelmanratkaisu
13. Syntaksi
konseptit
14. Syntax Error
poikkeukset
15. Stacktrace
Traceback
19. T
1. Taikaluku
Nimeämätön vakio
2. try-rakenne
Poikkeusten käsittely
3. Takaisinkutsu
funktiot
4. Terminal
työkalut
5. Testaaminen
konseptit ongelmanratkaisu
6. Text File
tiedostot
7. Tosi
arvot
8. True
Tosi
9. Traceback
ongelmanratkaisu
10. Tuple
tietorakenteet listat
11. Type Conversion
tyypit arvot funktiot
12. Tyylisääntö
13. Tyyppi
arvot konseptit
20. U
1. User Interface
konseptit
21. V
1. Variable
konseptit arvot
22. W
1. while
toistorakenteet
2. with
tiedostot
Completed: / exercises

4. Exercises: Modules of the End Times¶

These are the last exercises of the course. Think about that! But preferably only after you've thought about the exercises themselves. The topics today cover files and Python modules. The project-related exercises also offer quite fat chunks of code for the couse project.

Learning Goals¶

After this exercise you should be somewhat familiar with manipulating files. You'll also know quite a more bit about using modules, and also know how to make your own code work as a module. You'll also become familiar with the libary (or libraries) designed for the course project.

Example¶

As we promised in the material, this example covers the sweeperlib
library
that was made specifically for the course project. The example mostly covers how
handlers
behave with this library. It also continues from a couple of exercises in the sense that we're finally showing you how to implement movement using unit vectors.
Running the example requires Pyglet, which can be installed with
pip install pyglet

It would be fun to make an entire game prototype but that would involve a lot of things that are not necessary for this course. Instead, we're just going to make a simple, controllable game object. Let's set our goal to making a character that moves on its own and is animated, and it changes its direction when the player clicks somewhere on the screen. Let's also say that the character's movement speed isn't fixed, but instead accelerates upward from zero whenever the target point changes.

Solution¶

sweeperlib.py
The very first thing is to make something show up on the screen. This is where sweeperlib comes in to help. Its core principles are pretty much the same as the library we described in the material: the program's main loop runs Somewhere Else (tm), and the game logic itself is implemented in handler functions. This time around we just don't have interface components to attach our handlers to. If we take a look at sweeperlib, it can attach handlers of four types:
• mouse handler, which handles mouse clicks
• keyboard handler, which handles key presses
• draw handler, which handles draw
event
• interval handler, which is called repeatedly at given intervals
At minimum a game needs to have a draw handler in order for anything to be shown on the screen. Whereas our guilib did the drawing for us, this time we need to do it ourselves. This is because sweeperlib doesn't define premade game objects the same way guilib defines user interface components. The main responsibility of the draw handler is to draw each game object to a position on the screen tht matches its position in the game's logic. However, before we can actually draw anything we need to load some graphics. This step is not needed in minestomping because the library already contains a function to load the sprites that we've provided. Likewise there is no need to import pyglet in your own program, and specifically in this page's exercises you are not allowed to do that. For this example we need to create a separate function for loading two sprites (from the zip below) from the given
path
.
cross.zip
import pyglet
import sweeperlib

WIDTH = 800
HEIGHT = 600

pyglet.resource.path = [path]
sprites = {
"0": pyglet.resource.image("plus_1.png"),
"1": pyglet.resource.image("plus_2.png")
}
sweeperlib.graphics["images"] = sprites

We didn't choose the sprite
keys
arbitrarily - the reason will be revealed later. We also need the actual draw handler, which we'll implement by following the example at the end of sweeperlib - the whole process has been described in detail in the library's
docstrings
. We'll draw our sprite to 100, 100.
def draw_game():
sweeperlib.clear_window()
sweeperlib.draw_background()
sweeperlib.begin_sprite_draw()
sweeperlib.prepare_sprite("0", 100, 100)
sweeperlib.draw_sprites()

When these two functions are used in initializing the game and in the main program, we can see a prett plus sign on the screen. The handlers aren't attached to interface elements this time. Instead they're attached directly to the library itself by functions that exist for this purpose.
def start_game():
sweeperlib.create_window(WIDTH, HEIGHT)
sweeperlib.set_draw_handler(draw_game)
sweeperlib.start()

if __name__ == "__main__":
start_game()

The next step is to create some interactivity. We can start by making the game recognize the user's clicks, and react to them by teleporing the character to the spot. At this point we'll employ a familiar
dictionary
. As
handlers
still have the same issue we uncovered in the material, we cannot influence what arguments they receive. In other words, just like in the material, the game's state should be put into a
global
dictionary. We'll call it state, and place the dictionary that represents our character inside it with the "player"
key
.
state = {
"player": {
"x": 0,
"y": 0,
"speed": 0
}
}

The dictionary contains empty values of the correct type for each key. Once again the purpose is to show at a glance what attributes the game's characters have. Setting the values (to random position) is done in a separate create_player function.
def create_player():
state["player"] = {
"x": random.randint(0, WIDTH - 1),
"y": random.randint(0, HEIGHT - 1),
"speed": 0
}

Now that we have an object that has a position in the game logic, we can make a mouse handler that changes the position. The handler has four
parameters
although we only need the first two for x and y coordinates. The idea is the same as before: the handler changes values of the dictionary attached to the "player" key in the state dictionary. This makes the changes take effect everywhere this dictionary is used.
def handle_mouse(x, y, button, modifiers):
state["player"]["x"] = x
state["player"]["y"] = y

We also need to change the draw handler to draw the character where it actually is:
def draw_game():
sweeperlib.clear_window()
sweeperlib.draw_background()
sweeperlib.begin_sprite_draw()
sweeperlib.prepare_sprite("0", state["player"]["x"], state["player"]["y"])
sweeperlib.draw_sprites()

And finally use the new functions when starting the game:
def start_game():
create_player()
sweeperlib.create_window(WIDTH, HEIGHT)
sweeperlib.set_draw_handler(draw_game)
sweeperlib.set_mouse_handler(handle_mouse)
sweeperlib.start()

Basically this is enough information you need about handlers to implement a minesweeper. Majority of the game's logic will happen in handlers, and the functions they call. That said, this example doesn't quite yet match the specification, so we'll work on it a bit more. We wanted the character to accelerate towards the chosen point instead of teleporting to it. Because the character already has speed and heading, we need a click handler that changes the heading and sets the speed to zero. We also need to add acceleration as one attribute of the character.
The mouse handler becomes:
def handle_mouse(x, y, button, modifiers):
state["player"]["speed"] = 0

Setting the heading is best done in its own funcion because it sounds like something that would be useful in more than just this one context. There might even be more than one object in the game in the future! At this point we need to recall some basic trigonometry: if we know the base and height of a triangle, the angle is obtained with arctan, which has its own function in the math module. We just need to know that atan isn't good enough because it doesn't handle the signs of x and y separately - atan2 does.
def set_heading(character, target_x, target_y):
distance_x = target_x - character["x"]
distance_y = target_y - character["y"]

We don't have any real reason to convert angles to degrees here since they're never shown to players. We just did so because it makes the code a bit easier to digest. Especially if the program needs to be debugged at some point, and we need to investigate the headings of objects, degrees come in handy. Anyway, the player can now control the character. It just doesn't quite move yet. For this we need a third handler, one that updates the game state continuously, or approximately 60 times per second. The documentation of sweeperlib tells us that such a handler receives one argument: time elapsed since the last time it was called.
def update_game(elapsed):
state["player"]["speed"] += state["player"]["accel"]
update_position(state["player"])

You can find the update_position function called here from your own exercise solution. This solution relies on the game actually achieving 60 frames per second. If the game didn't achieve this, the game logic would slow down. A more correct solution would be to use the function's parameter so that all time-dependent values are multiplied by elapsed * 60 (which is exactly 1 if the game runs at 60 fps). We'll leave the code as is however, because it's a bit easier to read. When this handler is registered in the start_game function, we've achieved a controllable object.
def start_game():
create_player()
sweeperlib.create_window(WIDTH, HEIGHT)
sweeperlib.set_draw_handler(draw_game)
sweeperlib.set_mouse_handler(handle_mouse)
sweeperlib.set_interval_handler(update_game)
sweeperlib.start()

As a last curiosity, we'll show you how to do a two-frame animation. In order to do this, we need to add another key to the character dictionary. The value of this key indicates which sprite is shown currently. The keys for the sprites were "0" and "1" when we loaded them. In other words this key will always be inside [0, 2). We also need a constant to adjust the animation speed - a picture blinking 60 times per second is not pleasant to look at. With a value of 0.1 the sprite only changes 6 times per second.
ANIM_SPEED = 0.1

state = {
"player": {
"x": 0,
"y": 0,
"speed": 0,
"accel": 0,
"sprite": 0
}
}

Because we had the foresight to name the sprites "0" and "1" we can do the swapping with mathemagics. This is added to the update_game function. At each update the value of the sprite key is incremented by the animation speed constant, so that it takes 10 cycles from zero to one, and another 10 from one to two. Because there is no sprite number 2, we can wrap the cycling around to zero with modulo 2.
def update_game(elapsed):
state["player"]["speed"] += state["player"]["accel"]
state["player"]["sprite"] = (state["player"]["sprite"] + ANIM_SPEED) % 2
update_position(state["player"])

Again our game would be more stable if we multiplied the animation speed by elapsed * 60. The drawing handler also needs a change where it picks the sprite to draw from the dictionary. Because the value is a float from range [0, 2), it needs to be converted to an integer. The keys in the graphics dictionary are
strings
, but we peek inside the library it converts the sprite argument to a string - so we can give it integers. With this we've created a beautiful(?) animation. You can gaze at the result in amazement by downloading the program.
crossgame.py
import math
import random
import pyglet
import sweeperlib

WIDTH = 800
HEIGHT = 600
ANIM_SPEED = 0.1

state = {
"player": {
"x": 40,
"y": 40,
"speed": 0,
"accel": 0,
"sprite": 0
}
}

pyglet.resource.path = [path]
sprites = {
"0": pyglet.resource.image("plus_1.png"),
"1": pyglet.resource.image("plus_2.png")
}
sweeperlib.graphics["images"] = sprites

def create_player():
state["player"] = {
"x": random.randint(0, WIDTH - 1),
"y": random.randint(0, HEIGHT - 1),
"speed": 0,
"accel": 0.2,
"sprite": 0
}

def convert_to_xy(a, r):
x = int(round(math.cos(a) * r))
y = int(round(math.sin(a) * r))
return x, y

distance_x = target_x - character["x"]
distance_y = target_y - character["y"]

def update_position(char):
char["x"] += dx
char["y"] += dy

def handle_mouse(x, y, button, modifiers):
state["player"]["speed"] = 0
print(state["player"])

def update_game(elapsed):
state["player"]["speed"] += state["player"]["accel"]
state["player"]["sprite"] = (state["player"]["sprite"] + ANIM_SPEED) % 2
update_position(state["player"])

def draw_game():
sweeperlib.clear_window()
sweeperlib.draw_background()
sweeperlib.begin_sprite_draw()
sweeperlib.prepare_sprite(int(state["player"]["sprite"]), state["player"]["x"], state["player"]["y"])
sweeperlib.draw_sprites()

def start_game():
create_player()
sweeperlib.create_window(WIDTH, HEIGHT)
sweeperlib.set_draw_handler(draw_game)
sweeperlib.set_mouse_handler(handle_mouse)
sweeperlib.set_interval_handler(update_game)
sweeperlib.start()

if __name__ == "__main__":
start_game()


Common Exercises¶

As usual everyone needs to do these

Warmup Exercise¶

Spiraling Out of a File¶

This exercise continues the development of our a-spiraling code from last exercises. A new feature is to be added: it can draw by reading instructions from a file that contains multiple spirals. Each line in the file has the parameters of one spiral.
Learning goals: Reading from files, and converting file contents to variables.
Goal: A program that reads drawing instructions from a file and uses them along with the existing draw function to draw spirals.
Before You Begin:
You'll need to draw_spiral function from last week's spiral exercise. Copy it to your code file.
Function specification: draw_from_file
• Parameters
:
The function must open a
file
and read its lines that describe spirals. Each line has values in the same order as the draw_spiral function's parameters separated by commas:
• spiral's color (color value - either a color name or a hexadecimal color code)
• number of arcs to draw (integer)
• pen weight (integer)
The function needs to read these values from each line, convert them to correct types, and then call the draw_spiral function with them. Although pen weight is an optional argument, it is found on every line in the file - you can safely assume that each line will have 5 values.
In general you can freely assume that there are no errors in the file.
Use Examples:
Below is one example of a file that your function should be able to read. There's also a familiar picture that's been drawn based on this file.
spiral.txt
black,20,10,3,1
red,10,20,4,3
blue,10,-20,-4,3

Warning: You have not logged in. You cannot answer.

Main Exercises¶

Dunkin' Donkeygotchi¶

Some might still remember Tamagotchis or other virtual pets from way past. In this exercise you will implement your own virtual pet - a virtual donkey, of course.
This exercise teaches you how to work with a program made of more than one file, and with code made by someone else. We've included some of the donkeygotchi's modules. Your task is to finish the job by filling gaps in the main program and by creating the user interface module. The internal logic of the bit donkey has been already defined, along with a bunch of constants.
Learning goals: Reading code written by other people and completing it. Implementing your own
modules
. Using
dictionaries
and
constants
in code.
Goal: Make a user interface module for an otherwise functioning donkeygotchi.
Before You Begin:
This exercise uses two completed
code files
and one half-finished file. The files have the following roles:
• main.py: Main program module, functions as the program's "entrance" and implements the main loop that glues the program's logic together. This file has some placeholders marked with question marks that you have to fill in.
• donkeydefs.py: Contains predefined
constants
(like Python's math.pi) that can be used in other modules of the program.
• donkeylogic.py: The engine of the program that creates and manages data.
The code files can be found at the end under "Resources"
Unfinished module: main.py
The program cannot be ran before the placeholders in main.py have been filled in. What you need to do for each can be found out by looking at the donkeylogic and donkeydefs modules.
Module specification: donkeyinterface.py
• Docstring
:
• "Defines the donkeygothi's user interface."
• Functions
:
• show_state: (details below)
• prompt_choice: (details below)
1st function specification: show_state
• Parameters
:
• donkey's state in a data structure (dictionary)
This function prints the donkey's state, i.e. the values of age, money, satiation, happiness and energy. In addition, if the donkey has retired, a separate print is done to indicate this. The exact strings to use can be found from the examples at the end.
2nd function specification: prompt_choice
• Parameters
:
• donkey's state in a data structure (dictionary)
• Returns
:
• a valid input made by the user (string)
The function prints the available choices - based on the donkey's state - once, and then proceeds to prompt the user to make a choice until they give an input that is currently valid. If the donkey is not retired, the valid inputs can be found from the CHOICES list in the donkeydefs module; if the donkey is retired, valid inputs are in the RETIRED_CHOICES list. These constants should be used for both printing the available choices, and validating inputs. All strings to use in prompts and prints can be found from the examples.
Use Examples:
The donkey is 96 years old and has 0 eur.
Satiation: 5
Happiness: 5
Energy: 5
Choices: q, f, w, t
Input next choice: q

The donkey is 96 years old and has 0 eur.
Satiation: 5
Happiness: 5
Energy: 5
Choices: q, f, w, t
Input next choice: Z
Invalid input!
Input next choice: ???
Invalid input!
Input next choice: w
The donkey is 97 years old and has 1 eur.
Satiation: 5
Happiness: 5
Energy: 5
Choices: q, f, w, t
Input next choice:

The donkey is 100 years old and has 12 eur.
Satiation: 6
Happiness: 9
Energy: 2
The donkey has retired.
Choices: q, r
Input next choice: X
Invalid input!
Input next choice: f
Invalid input!
Input next choice: t
Invalid input!
Input next choice: r
The donkey is 0 years old and has 0 eur.
Satiation: 5
Happiness: 5
Energy: 5
Choices: q, f, w, t
Input next choice:

Resources:
donkeylogic.py
"""
Defines the donkeygotchi's internal logic
"""
import donkeydefs as defs

def init():
"""
Initializes donkey data by creating a new dictionary with initial values for
all keys, and returns it.
"""
donkeydata = {
"SATIATION": defs.INITIAL,
"HAPPINESS": defs.INITIAL,
"ENERGY": defs.INITIAL,
"AGE": 0,
"MONEY": 0,
"RETIRED": False,
}
return donkeydata

def _age(donkeydata):
"""
Ages the donkey and - if needed - puts it in retirement. Meant only for
internal use in this module.
"""
donkeydata["AGE"] += 1

if donkeydata["AGE"] == defs.RETIREMENT_AGE:
donkeydata["RETIRED"] = True

def _update_states(donkeydata):
"""
Changes the donkey's state as time passes, and puts the donkey in retirement
if needed. Meant only for internal use in this module.
"""
if donkeydata["AGE"] % 2 == 0:
if donkeydata["SATIATION"] > 6 and donkeydata["ENERGY"] < defs.MAX_STATE:
donkeydata["ENERGY"] += 1
donkeydata["SATIATION"] -= 1
if donkeydata["AGE"] % 3 == 0:
donkeydata["HAPPINESS"] -= 1

if donkeydata["SATIATION"] <= 0 or donkeydata["HAPPINESS"] <= 0 or donkeydata["ENERGY"] <= 0:
donkeydata["RETIRED"] = True

def feed(donkeydata):
"""
Feeds the donkey, i.e. raises its satiation, if it isn't at the maximum yet.
"""
_age(donkeydata)
_update_states(donkeydata)
if donkeydata["SATIATION"] < defs.MAX_STATE:
donkeydata["SATIATION"] += 1

def tickle(donkeydata):
"""
Tickles the donkey, i.e. raises its happiness, it it isn't at the maximum yet.
"""
_age(donkeydata)
_update_states(donkeydata)
if donkeydata["HAPPINESS"] < defs.MAX_STATE:
donkeydata["HAPPINESS"] += 1

def work(donkeydata):
"""
Makes the donkey work by spending its energy in return for money.
"""
_age(donkeydata)
donkeydata["ENERGY"] -= 1
donkeydata["MONEY"] += 1
_update_states(donkeydata)

donkeydefs.py
"""
Defines the variables that are used in the donkeygotchi.
"""

# input choices
QUIT = "q"
FEED = "f"
TICKLE = "t"
WORK = "w"
CHOICES = [QUIT, FEED, TICKLE, WORK]

RESET = "r"
RETIREMENT_CHOICES = [QUIT, RESET]

# Aasin tilat
INITIAL = 5
RETIREMENT_AGE = 100
MAX_STATE = 10

main.py
import ???
import ???
import ???

def main():
donkeydata = donkeylogic.???

while True:
donkeyinterface.show_state(donkeydata)
choice = donkeyinterface.prompt_choice(donkeydata)

if choice == donkeydefs.QUIT:
break
elif choice == donkeydefs.FEED:
???
elif choice ==  donkeydefs.TICKLE:
???
elif choice == donkeydefs.WORK:
???
elif choice == donkeydefs.RESET:
???

if __name__ == "__main__":
???

return donkeyinterface.py and main.py. You can choose more than one file in the browser's upload dialog by pressing Ctrl down when choosing.
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Course Project Exercises 1¶

Choose one of these. Note that there's only two choices here: minestompers should pick the first one, others the second one. This is because the spectrum and circuit projects use the same library to create their user interface.

Time to Mousey¶

Who would play a text-based terminal minesweeper in the 2000s? This exercise along with the following ones give you a basis that allows you to implement a beautiful Minestomper with real graphics and mouse controls. We've given you a custom library for this purpose, and this exercise starts your journey in getting familiar with it. The topics are application windows and handler functions.
Learning goals: Creating a window. Handling the mouse with sweeperlib. Implementing and using a handler function.
Goal: A program where the mouse handler tells where inside the window mouse was clicked.
Before You Begin:
This exercise uses the library we made for the Minestomper course project. It helps rather significantly in implementing a graphical interface. Download the library if you don't have it yet and explore it carefully. The library comes with rather extensive docstrings and a short example at the end.
sweeperlib.py
The Minestomper project page also contains some explanations about how to use the library - definitely worth a read at this point. You should also install Pyglet if you haven't already.
Note that in order to complete this exercise your code does not need to import Pyglet - all interaction with Pyglet is done through sweeperlib. The checking server doesn' even have Pyglet so trying to import in your code causes a ModuleNotFoundError exception. In the course project itself you can do what you want however.
1st function specification: handle_mouse
• Docstring
:
"""
This function is called when a mouse button is clicked inside the game window.
Prints the position and clicked button of the mouse to the terminal.
"""

• Parameters
:
• x coordinate of the mouse (integer)
• y coordinate of the mouse (integer)
• mouse button (integer)
• pressed modifier keys (integer - not used in this exercise but needs to be defined in order for the function to be callable)
The function prints its parameers to the terminal (see examples for formatting). The mouse button is an integer where each value corresponds to a different button. You don't need to memorize these values because you can use the sweeperlib constants MOUSE_LEFT, MOUSE_MIDDLE, and MOUSE_RIGHT to know which button was clicked. You can practice dictionaries by making one where these constants are the
keys
and strings "left", "middle", and "right" are their values.
2nd function specification: main
• Docstring:
"""
Creates a game window and sets a handler for mouse clicks.
Starts the game.
"""

The main function has to create a window using the sweeperlib's create_window function, and set a mouse handler using the set_mouse_handler function. Study how these functions work. You can choose the size of the window freely. Background color doesn't matter because the window is not drawn after being created. At the end the application needs to be started with the start function.
Main Program Specification:
if __name__ == "__main__":
main()

Use Examples:
These examples only show what is printed to the terminal.
The left mouse button was pressed at 123, 53
The right mouse button was pressed at 20, 10
The middle mouse button was pressed at 250, 39

Return the file you created, no other files.
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Just an Ordinary Window¶

In order to see spectrums and circuits running you need to learn the basics of graphical user interfaces. This is the first exercise in the series. It will teach you how to create a basic interface with a couple of components. A small library will assist you in this quest, allowing you to survive with a few simple function calls.
Learning goals: The basics of creating a use interface window. The basics of the guilib library used in the course project.
Goal: A program that creates an interface window.
Installation: matplotlib
The guilib module requires matplotlib in order to work. You can install it with the pip program by giving this command: pip install matplotlib. Pip is usually included with Python. See pre-exercises if you don't remember how to use it. In some Linuxes and in Mac OS X the command can be pip3 - pip alone installs for Python 2.
Before You Begin:
The exercises uses the guilib module that is also used in Spectral Matters and Run, Circuit! Run! The library contains functions that allow you to create simple user interfaces. Download the library from the link below and study it carefully. It contains extensive docstrings and an example program at the end.
guilib.py
The first thing you should do is to test the library by running it. If you get a message about a missing DLL, it's very likely this one and you need to install it.
The course project page also gives a short introduction to graphical user interfaces. Should be a worthy read at this point.
Note that you do not need to import either Tkinter or Matplotlib into your own program - everything happens through guilib. These haven't been even installed on the checking server which means you will get ModuleNotFoundError exceptions if you try to return code that imports them.
Finally, create this dictionary into your program, it will contain references to the UI components.
widgets = {
"textbox": None
}

Because the program is mostly based on handler functions you have no control over what parameters they can have. Therefore the program's state and references to components must be kept
globally available
. The best way to manage that is to collect everything into a dictionary that can be accessed from all functions.
1st function specification: print_testline
• Docstring
:
"""
Prints a test line into a textbox in the user interface.
"""

When the function is called it writes e.g. "donkeyswings" (doesn't matter, write what you want) to a textbox in the widgets dictionary. Use the library's write_to_textbox function. The message contents don't matter, its purpose is to just show that the UI components have been connected to each correctly.
2nd function specification: main
• Docstring:
"""
Creates an application window with two buttons on the left and one textbox on
the right. Text can be printed to the box by pressing a button.
"""

The task of the main function is to create the interface components, connect handlers to buttons, and finally start the program. We want a window with two frames: on the left there should be two buttons, and on the right a textbox. The first button should be connected to the print_testline function we just created. The second button's handler is the library's quit function. You can choose the text on the buttons.
When you create the textbox, assign it to the previously defined dictionary.
You need the create_window, create_frame, create_button, and create_textbox functions from the guilib. The examples section shows a screenshot of the completed interface. Exact measurements might differ from your version but the layout must match.
Main Program Specification:
if __name__ == "__main__":
main()

Use Examples:
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Course Project Exercises 2¶

Choose on of these.

Mine Time¶

Randomness is a rather important aspect in games, and in general important enough to have its own programming tools. This exercise will help you when it's time to generate a mind field in the Minestomper course project. You'll also learn about drawing graphics with game libraries.
Learning goals: Getting familiar with the random module and implementing a suitable randomization for mine placement. The basics of drawing game graphics. Implementing a draw handler with the sweeperlib module.
Goal: A program that places a specified number of mines into random tiles in a field, and shows the result in a game window.
Before You Begin:
This exercise uses the same sweeperlib module as the previous one. In addition you will need the minestomper graphics package and unpack its contents into a folder of your choice.
Because the draw handler cannot have any parameters, it's not possible to hand the field to it as an argument. Therefore the field needs to be made available to all functions in the program through some other means. In this exercise we'll use a dictionary that holds the game state - this is the best way to do this with our current knowledge. Place the following snippet into your code immediately after imports:
state = {
"field": []
}

Naturally the empty list will be replaced with a two-dimensional list that represents the field once the program is running. Note that the checker requires your program to have this dictionary.
1st function specification: place_mines
• Docstring
:
"""
Places N mines to a field in random tiles.
"""

• Parameters
:
• field to mine (2-dimensional
list
)
• list of available tiles (list of coordinate pair
tuples
)
• number of mines to place (integer)
The function chooses N coordinate pairs from the list of available tiles and places a mine into each of the selected tiles in the field (mine is marked with "x"). This can be done in multiple ways - just make sure not to mine the same tile twice! Mined coordinate pairs should therefore be removed from the list of available tiles.
2nd function specification: draw_field
• Docstring:
"""
A handler function that draws a field represented by a two-dimensional list
into a game window. This function is called whenever the game engine requests
a screen update.
"""

Open sweeperlib.py and read the docstring of set_draw_handler to learn how to implement a draw
handler
. The field must be retrieved from the state dictionary using the "field" key. When drawing tiles, you need to multiple their list indices by the size of the tile sprite (which you can see by looking at the tile image file properties). The part where you iterate through the field will be very similar to a previous exercise.
3rd function specification: main
def main():
"""
Loads the game graphics, creates a game window and sets a draw handler for it.
"""

sweeperlib.load_sprites(#you need the path to the sprites folder here)
sweeperlib.create_window(600, 400)
sweeperlib.set_draw_handler(draw_field)
sweeperlib.start()

Main Program Specification:'
The main program must be placed inside the if __name__ == "__main__":
conditional statement
. The main program's purpose is to test your functions. This is done by creating a 15x10 field where we place 35 mines. The mines are placed by
calling
the place_mines function once. The field can be created with this snippet:
field = []
for row in range(10):
field.append([])
for col in range(15):
field[-1].append(" ")

state["field"] = field

In addition you need the aforementioned list of available coordinates. This can be created with the following snippet. Pay attention to the connection between dimensions, rows, columns, and coordinates.
available = []
for x in range(15):
for y in range(10):
available.append((x, y))

After this you should first call your place_mines function, followed by the main function.
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Pointing is Rude...¶

...but oh so practical - at least when it comes to pointing things on the screen with a mouse. This exercise teaches you a couple of skills that will be important in Spectral Matters: displaying a figure inside an application window, and reading mouse clicks from it.
Learning goals: Drawing a figure using matplotlib and guilib together. Implementing a mouse handler for the figure. Storing event information to program memory.
Goal: A program that draws a figure, and reports the x and y data values of the clicked point.
Before You Begin:
A figure embedded into an application window consists of two parts: the figure itself, and the canvas. Our guilib's create_figure returns both of these - your task is to draw using them. The former is a matplotlib Figure object - it's documentation is here. Note that the figure itself cannot be drawn to - you need to create a subplot for it first (an axes object). In some cases the figure is not displayed until the canvas object's draw method is called - you need to do this in your code even if you can see the figure without it.
The mouse
handler
follows the same principles as the button handler from the last exercise but it does have one parameter: a mouse event (documentation). This event is an
object
with a few important
attributes
. The key ones are:
• x and y which are the screen coordinates that were clicked
• button, the button that was clicked (1 = left, 2 = middle, 3 = right)
• xdata and ydata that are the axis values in the clicked point
The exercise also needs a similar
dictionary
as the last one but due to its broader nature, we'll name it state
because it contains general information about the program's state. A new key-value pair is added to the dictionary. You should save all clicked data values to this value as
tuples
.
state = {
"textbox": None,
"points": []
}

1st function specification: choose_point
• Docstring
:
"""
Receives a mouse event from a mouse click and reads the x and y data
values from it. The values are printed into a textbox, and saved to a list
in the program's state dictionary.
"""

• Parameters
:
• mouse event (matplotlib MouseEvent object)
The function needs to read the axis values from the mouse event it receives. These values are in the xdata and ydata attributes. The values are written into the textbox with two decimal precision - see the message format from the examples. This point should also be appended to the points list inside the state dictionary. This is important because in the course project you need to access previously selected points. When points are saved into the state dictionary like this, they are conveniently available.
2nd function specification: main
• Docstring:
"""
Creates a user interface that contains an interactive figure and a textbox.
A plot based on data received as parameters is drawn into the figure.
"""

• Parameters:
• x axis data (list of floats)
• y axis data (list of floats)
This function has the same purpose as the one in the previous exercise. This time the the interface is split vertically. The upper frame contains the figure. You can check the create_figure docstring for information on how to add one. The handler should be the choose_point function we just implemented. The bottom frame contains the familiar textbox. In addition the function should plot the data it receives.
An example of the result can be found at the end.
Main Program Specification:
if __name__ == "__main__":
datax = [0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0]
datay = [0.0, 0.19, 0.36, 0.51, 0.64, 0.75, 0.84, 0.91, 0.96, 0.99, 1.0, 0.99, 0.96, 0.91, 0.84, 0.75, 0.64, 0.51, 0.36, 0.19, 0.0]
main(datax, datay)

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Coder's Complex¶

We've already learned that Python will happily eat complex numbers. Last time we handled them in the terminal but how about prompting numbers in a graphical interface? This might be needed in Run, Circuit! Run! so it should be learned at some point. We can learn about error messages while we're at it.
Learning goals: Prompting and handling user inputs in a graphical user interface.
Goal: A program that calculates polar presentation for complex numbers.
Before You Begin:
You can use the interface from the previous exercise as a base. A new dynamic component is added to the program to keep company for the lonely textbox: a text field where the user can type a complex number. Like before, a referenced to this new component should be saved into a dictionary so that it can be accessed from a handler function. Start the program with the following dictionary:
elements = {
"textbox": None,
"textfield": None
}

1st function specification: convert_to_polar
• Docstring
:
"""
Reads a complex number from an input field and converts it to polar
representation, using degrees for the angular component. The complex number
and its polar representation are written into a textbox.
"""

This is
handler
and therefore doesn't have any parameters, nor does it return anything. The input is read from a text field that can be accessed through the elements dictionary (guilib has a function for reading text fields). If the user's input isn't a valid complex number, they are notified about the error with a popup window. There's a function for this as well in the library.
The conversion
function
itself should be already familiar. Once again the angle has to be converted from radians to degrees. The result is written into the textbox as seen in the examples. All floats are presented with three decimal precision.
Whether the conversion was successful or not, the handler should clear the input field once it's done.
2nd function specification: main
• Docstring:
"""
Creates a user interface window with text field and two buttons on the left
side, and a textbox on the right side.
"""

The main function is based on the last exercise. The new additions are the aforementioned text field to the left frame, and an instruction label above it (that says e.g. "Complex number:"). Remember to assign the value returned by the creation function to the elements dictionary. The test button is replaced by a conversion button which uses the function we just implemented as its handler.
Main Program Specification:
if __name__ == "__main__":
main()

Use Examples:
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Course Project Exercises 3¶

And finally choose on of these.

Flood Survey¶

Floodfill is a basic algorithm that has all kinds of uses in programming. For instance it can be used to determine the size of any limited area with arbitrary shape. The fill tool of drawing programs is also based on it. Floodfill can also be used to navigate labyrinths or calculate how far a game character can move in varied terrain. Coincidentally it also plays a critical role in Minestomping where there's a need to open empty tiles in a way that expands to every direction without revealing the mines. It's not the easiest algorithm to figure out without any programming experience so we've included a step-by-step guide into this assignment.
In this exercise a probe droid is exploring the surface of a planet ja marking unknown territory as safe while avoiding areas that were previously marked as dangerous.
Learning goals: Understand how the floodfill algorithm works and learn about implementing somewhat complex algorithms in Python. Removing items from lists without turning the program into a slog.
Goal: A program that explores connected unknown tiles on a map.
Before You Begin:
You can draw the field similarly as in the last exercise. Grab the draw_field function from there. The main function is also mostly the same (see below).
1st function specification: floodfill
• Docstring
:
"""
Marks previously unknown connected areas as safe, starting from the given
x, y coordinates.
"""

• Parameters
:
• the planet to explore (2-dimesional
list
)
• starting point x coordinate (integer)
• starting point y coordinate (integer)
The map of the planet contains two kinds of characters: unknown " " and dangerous "x". A safe tile is marked with "0". Your task is to start from the initial point and proceed to mark all connected tiles as safe. If the initial point is dangerous, nothing is done. You need to follow the provided step-by-step instructions for the algorithm quite accurately. In particular you need to avoid using
recursion
(you know you're using it if your floodfill function calls itself at any point)
.
The floodfill is started by creating a list with one item: a tuple that contains the starting point's coordinates. After initializing the list, the program moves on to a
loop
that runs until the entire connected area is filled. Each
iteration
of the loop proceeds as follows:
1. a new item is taken for processing from the aforementioned list (note: it has to be removed) - there's a method for this
2. it is marked as safe by replacing the character in those coordinates of the planet list with "0"
3. iterate through all surrounding coordinates (8 total, but be mindful of borders!) (see the ninja exercise for how to do this)
4. each tile that is unknown is added to the aforementioned list
This way the list that contains coordinate pairs keeps growing at the same time as it is consume, and only becomes entirely empty once all connected unknown tiles have been explored. Marking a tile as safe is done at the beginning of each iteration. We know the tile is safe because it was added to the list on a previous iteration, and the algorithm only adds unknown tiles to the list.
The function doesn't return anything.
2nd function specification: main
• Docstring:
"""
Loads the game graphics, creates a game window, and sets a draw handler
"""

• Parameters:
• planet (a list that represents the planet, see below)
This function is based on the previous main function. We do note however that the planet shown below does not fit nicely into a 600x400 window. Change the window size accordingly - the best way to do this is to use the len function to get the field's dimensions and multiply them with the sprite dimensions.
Main Program Specification:
You need a main program that calls your functions for testing. You can use the following planet in your main program:
planet = [
[" ", " ", " ", "x", " ", " ", " ", " ", " ", " ", " ", "x", " "],
[" ", " ", "x", "x", " ", " ", " ", "x", " ", " ", " ", "x", " "],
[" ", "x", "x", " ", " ", " ", " ", "x", " ", " ", "x", "x", " "],
["x", "x", "x", "x", "x", " ", " ", "x", " ", "x", " ", " ", " "],
["x", "x", "x", "x", " ", " ", " ", " ", "x", " ", "x", " ", " "],
[" ", " ", "x", " ", " ", " ", " ", " ", " ", "x", " ", " ", " "]
]

Call the floodfill function with a suitable starting point. Finally call the main function so you can see what the floodfill did.
Speed Requirements:
Unlike every exercise in this course, this one will actually reject a solution that is too slow. You will know this from a message that says "Stopped responding and timed out after 10,01 seconds." underneath the executed command, and the checking log itself will be empty. The primary cause for slowness is bad removal of items from the list. If items are removed from the beginning or middle of the list, a chain reaction is caused where all the remaining list indices must be updated (imagine the items being placed one slot closer to the beginning, one at a time). You won't notice the difference with a small field, but will notice with the 100x100 field included in the tests. Removals must be done from the end of the list.
Furthermore, remove is not a good method in this task beause it removes the first matching item from the list. This becomes a problem because the algorithm can place the same coordinate pair multiple times into the list. So even if you try to remove the last item, it is likely that one of its copies earlier in the list gets removed instead. Investigate list methods and find a more suitable method for this task.
Another way to make the checking time out is to make an
infinite loop
. For instance if your algorithm doesn't make sure it doesn't enter tiles it has already visited, it will end up visiting the same tiles over and over infinitely.
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Dataminer in the Junkyard¶

This exercise teaches you a basic skill that is required for all kinds of data processing: reading data files. You've received a request from a researcher who konws nothing about programming. In addition they are very, very messy with their files - the data folders can include all kinds of trash like vintage meme pictures. Some data files are broken too. In general it's preferable for data readers to be able to find the real data from somewhat less organized folders. Program requirements are hard to keep in mind when saving things to the hard drive without much thought.
Learning goals: Reading data from multiple
files
to
data structures
in a program. Figuring out broken files and the correct way to handle them. Reading data rows.
Goal: A program that reads data from multiple files to program memory.
Before You Begin:
To make this task seem a bit more relevant we've given you a script that creates a bunch of random data files. All files generated by the script are intact, so you have to break some of them manually. While you're at it, copy your holiday pictures into the same folder to confuse your program a bit more. Run the script in the terminal with a
command line argument
that indicates which folder you want the data to go to.
generate_data.py
import os
import sys
import random

NAMES = ["Squall", "Cloud", "Celes", "Yuna", "Pikachu", "Bulbasaur", "Winnie the Pooh", "Eeyore", "Eunji", "Tomomi", "Haruna", "Seungyeon", "Ihsahn", "Abbath", "Fenriz"]

CHARS = "abcdefghjiklmnopqrstuvwxyz"

def gen_data(folder):
os.makedirs(folder, exist_ok=True)
for i in range(10):
with open(os.path.join(folder, "".join([random.choice(CHARS) for x in range(random.randint(4, 10))]) + ".mydat"), "w") as target:
for i in range(random.randint(4, 20)):
target.write("{},{:.4f},{:.4f}\n".format(
random.choice(NAMES),
random.random() * 1000,
random.random() * 100
))

if __name__ == "__main__":
try:
gen_data(sys.argv[1])
except IndexError:
print("Usage:")
print("python generate_data.py folder")

You can also copy the main function from the Just an Ordinary Window exercise.
1st function specification: read_data
• Docstring
:
"""
Reads all data files from the given folder. Skips files that don't have the
.mydat extension and files that have errors in them. The names of faulty .mydat
files are reported to the user.
"""

• Parameters
:
• target folder's path (
string
)
• Returns
:
• contents of the data files as a
data structure
(list of 3 item tuples)
• names of faulty .mydat files (list of strings)
The function has to go through the contents of the folder and find all all .mydat files, and read their contents (other files are skipped silently). Data is appended to the program's data structure only when the end of each file is reached. If an error is encountered while reading a file, all data from that file is discarded, and the file's name is added to the list of faulty files. Correct data rows will look like:
Tomomi, 154.3578,12.9402

In other words each data row has three comma-separated values. The first one is always string. Each data row is parsed into a
tuple
that contains a string, and two
floats
, e.g.:
("Tomomi", 154.3578,12.9402)

These tuples should be appended to a temporary list first, and only added to the actual data list when the entire file has been read. This data list is returned when all files have been processed. You should also keep in mind that files may or may not have an empty line at the end. Depending on your implementation this can require additional processing.
2nd function specification: open_folder
• Docstring:
"""
A button handler that opens a dialog the user can use to choose a data folder.
Loads data from the selected folder and reports the number of rows read and the
names of any faulty files into a textbox.
"""

This function should open a folder dialog (with a guilib function), and use its return value to call the read_data function. When the data has been read, the names of all faulty files are written (e.g. as "Faulty file: x") to the textbox, and finally the number of data rows read.
Function modification: main
Change the test button's label to "load" or something else descriptive, and the handler to the open_folder functin.
Main Program Specification:
if __name__ == "__main__":
main()

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A Circuitful of Resistors¶

This exercise is about drawing simple circuit diagrams inside the application window. You're probably shocked to know that this knowledge is needed in the Run, Circuit! Run! course project. In this program the user enters a bunch of resistors to the circuit, and the circuit diagram is updated whenever something is added to it. Once again we have a helper library that simplifies this process to a level that suits this course.
Learning goals: Using the circuitry module to draw circuit diagrams. Prompting and saving components in a graphical user interface.
Goal: A program that prompts for serial-connected resistors and draws them along with a voltage source.
Required installation: SchemDraw
The actual worker behind the scenes for drawing circuits is the SchemDraw module. Installation process is the same as for matplotlib (i.e. pip install SchemDraw. You can look into the library in its documentation but this is not required because we're using a helper library.
Before You Begin:
You also need two more modules that were created for this course: the circuitry module which includes circuit drawing functions, and SchemCanvas which allows SchemDraw to draw inside the application window. You don't need to look at the SchemCanvas module, it goes quite a bit beyond this course.
circuitry.py
SchemCanvas.py
Once again it's a good idea to define a dictionary at the beginning of the code for storing references and values during execution.
state = {
"textfield": None,
"textbox": None,
"circuit": None,
"components": [],
"voltage": 0,
"frequency": 0,
}

1st function specification: set_voltage
• Docstring
:
"""
Reads a float value from an input field and sets it as the circuit's voltage.
"""

This is a handler function that tries to read a number from the textfield and save it to the state dictionary. If the field doesn't contain a valid number, a message is displayed with a popup window similarly to the last exercise. It's also considered good manners to clear the field after reading its value. To keep the UI responsive, it should also report the new voltage in the textbox.
2nd function specification: set_frequency
• Docstring:
"""
Reads a float value from an input field and sets it as the circuit's frequency.
"""

Same as above but for frequency.
3rd function specification: add_resistor
• Docstring:
"""
its resistance. The resistor is added to the sole loop in the circuit.
"""

Same as the two above, but instead of saving the value directly, a new item is added to the components list: a two value tuple where the first item is "r" and the second is the float value. After adding the resistor, the circuit diagram needs to be updated using the draw_voltage_source, draw_loop, and draw_circuit functions.
SchemDraw is intended for drawing a complete circuit and doesn't directly support updating the diagram once it's ready. Therefore whenever something needs to be added to the circuit, the diagram needs to be cleared entirely and redrawn from the beginning. Since drawing the circuit always start form the voltage source, the reset happens when draw_voltage_source function is called. Loops are drawn one at a time. The circuitry module does most of work in component layout but you may need to do some fine adjustments (only in the course project though, this exercise is rather straightforward in terms of layout). Note that these functions only prepare the circuit diagram - it is drawn only when the draw_circuit function is called.
Study the functions mentioned here to understand how they work.
Invalid component value should give an error message in the form of a popup window.
4th function specification: main
• Docstring:
"""
Creates a user interface window with input field, four buttons, and a textbox
on the left side. The right side contains a circuit diagram.
"""

The interface is created in the same way as previously. Buttons are connected to the functions made in this exercise. References to the textfield, textbox, and circuit diagram are stored to the state dictionary. You should set suitable dimensions for the textbox and circuit diagram yourself.
Main Program Specification:
if __name__ == "__main__":
main()

Use Examples:
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1. Description
2. Examples
Absolute path is an operating system term that refers to the full "address" of a file or folder. Absolute path is written starting from the disk root. When absolute path is used, the current directory does not matter. Absolute paths are usually avoided in code - especially in applications that are meant to be shared. Another user is very unlikely to have the exact same folder structure as the application's developer. In particular if an absolute path refers to the user's home folder, it is very likely not going to be the same for another user.
Ajonaikaisesta (engl. run time) puhuttaessa määreenä on se aikaväli, kun ohjelma on käynnissä. Esimerkiksi Pythonissa virheet (syntaksivirheitä lukuun ottamatta) tarkastetaan ajonaikaisesti. Ohjelma saattaa siis olla käynnissä ja toimia tiettyyn pisteeseen saakka, kunnes törmätään käsittelemättömään poikkeukseen – ajonaikaiseen virheeseen (engl. run time error).
1. Description
2. Esimerkit
Alustamisella (engl. initialize) tarkoitetaan yleisesti jonkin arvon asettamista muuttujalle muuttujan luonnin yhteydessä. Pythonissa ei ole mahdollista luoda muuttujaa, jolla ei ole myös jotain arvoa. Niinpä tyypillisesti käytetäänkin sanamuotoa ”muuttuja alustetaan arvolla x”, millä tarkoitetaan sitä, että muuttuja, joka luodaan, saa luomisen yhteydessä (eikä vasta joskus myöhemmin) arvon x.
1. Description
2. Esimerkit
Argumentti (engl. argument) on funktiokutsussa käytettävä arvo, joka välitetään kutsuttavalle funktiolle. Funktiokutsun alkaessa argumentit sijoitetaan parametreiksi kutsuttuihin muuttujiin, joiden kautta arvoihin pääsee funktion sisällä käsiksi.
Arvo (engl. value) on konkreettista, tietokoneen muistissa sijaitsevaa tietoa, jota käytetään ohjelman suorituksen aikana. Arvoilla on tyyppi ja sisältö; esimerkiksi numero 5 on tyypiltään kokonaisluku, jonka sisältö on 5. Useimmiten arvot liitetään muuttujiin, mutta myös operaatioiden ja funktiokutsujen paluuarvot sekä koodissa sellaisenaan esiintyvät arvot ovat arvoja. Käytännössä siis kaikkea konkreettista mitä ohjelma käsittelee voidaan kutsua arvoiksi.
Assignment is related to variables and values. A typical figure of speech is "assigning to a variable" which means giving a certain value to a variable (e.g. x = 5). More specifically, in Python, assignment to a variable means creating a connection between the name and value of the variable - the variable is a way to find the value.
Similar expressions that can be used to mean the same thing are: "saving to a variable", "storing to a variable", "referring to a variable", "stuffing a value into a variable"... etc.
Assignment operator i.e. the = character is used for variable assignment. When using the operator, the target variable must always be on the left side and the value (or statement that produces the value) on the right side.
Attribute is a value that belong to an object, sometimes also called property. It's a name that belongs to the object's internal namespace and it can be accessed through the object: timestamp.tm_hour would read the hours from a timestamp.
1. Description
Avainsanat (engl. keyword) ovat ohjelmointikielessä kielen käyttöön varattuja sanoja, joilla on erityinen merkitys. Hyvät tekstieditorit tyypillisesti merkitsevät avainsanat muista nimistä eroavalla tavalla (esimerkiksi lihavoinnilla tai tietyllä värillä). Avainsanat ovat yleensä suojattuja, eli samannimisiä muuttujia ei voi luoda. Yleisiä avainsanoja Pythonissa ovat esimerkiksi funktioihin liittyvät def ja return. Avainsanat ovat siis osa ohjelmointikielen kielioppia.
Boolean is the most simple data type in programming languages because it has only two values: true (True in Python) and false (False in Python). Things like comparison operators return booleans, and they are often used in conditional statements and while loops. In Python all values are equivalent to one of the boolean values. Generally all so called empty values (0, "", None etc.) are equal to False while the rest are equal to True.
1. Description
2. Extra info
Boolean operator refers to Boolean algebra which deals in values of truthfulness. These operations include and, not, and or - all familiar from conditional statements. Out of these and is True if and only if both operands are True; or is True if at least one operand is True; and not is True is its sole operand is False.
Branch is an execution path in the program that is mutually exclusive with other branches in the same control structure. For example in a conditional structure each if, elif and else define their own branches and only of them is executed.
Bug is an error in the program's source code. As the result of a bug the program either doesn't start at all, crashes during execution, doesn't work correctly in some situations, or can even cause severe security issues. Careful programming and testing - including rare edge cases - reduces the probability of bugs. Tracking down the part of code that causes a bug and fixing it is called debugging.
Buitin functions are function that are included in the Python core. They can always be used without importing any modules or libraries.
Callback is a common mechanism, especially in modern programming, where another part of the program - often made by someone else - is given a function it is to call during its execution. If a normal function call is like a phone call, a callback is a like a call request. If a part of the program uses a callback, it usually described what kind of a function it accepts - especially what parameters the function can/must have and what kind of a value it should return.
Where UNIX-based systems produce \n characters (newline) to indicate line breaks, Windows uses \r\n where the r is a carriage return character. It's a remnant from mechanical typewriters, and indicates the procedure of physically moving the typewriter head to the beginning of the line. In general this is just something that's good to know - Python treats both line breaks quite nicely.
Code block or block is a term used for liens of codes that belong to the same context. A block is formed of lines that have the same indentation level (although a block can also contain other blocks). Typical blocks are the executable parts of conditional structures i.e. the indented code lines that follow a condition. A block ends when a line with less indentation than ones belonging to the block is encountered.
Code file is a text file that contains executable code. A Python code file can be ran from the terminal by typing python code.py where code.py is the file's name. When you run a code file the return values of individual lines are not shown unless they have been specfically rpinted.
1. Description
2. Material example
3. Basic use
Command line argument or parameter is a name used for additional information that is passed to a terminal program when it's started. Command line arguments are typically separated by spaces. E.g. in python code.py, code.py is actually a command line argument. Command line arguments can be accessed in Python from the sys module's argv variable.
Comparison operators are used for comparing values to one another. They are familiar from mathematics and can be used to compare size. Comparison operators return a boolean value, True or False, depending on the result of the comparison. Comparison operators are: <, <=, >, >=, == and !=
Comparison values are used e.g. in sorting lists. A comparison value is a value derived from a list item that is used instead of the item itself in sorting. For instance, if a list contains lists, a comparison value can be an item taken from a certain index of each inner list. It can also be a more complex derivative such as the sum of items or their mean value.
1. Description
2. Examples
Condition is used in this course to refer to the part of conditional statements and while loops that defines when the statement is true. Anything between the keyword that starts the stamement and the colon that ends it is basically its condition.
1. Description
2. Examples
Conditional statement is a line of code that defines a single condition, followed by an indented code block which defines what should be done if the condition is true. Conditional statements include if and elif statements, the latter of which cannot be present without the former. Conditional statements that are linked together form conditional structures. A conditional statement must always end with a colon and it must be followed with at least one indented code line.
1. Description
2. Examples
Conditional structure is a structure that consists of one or more conditional statements that branches program execution. Most of them have at least two branches: if and else. Between the two there can also be an indefinite number of branches under elif statements. It is also possible to have nothing but a single if statement in a structure. Each branch in a conditional structure has at least some code that defines what the program does in a situation falling under a condition.
As a whole a conditional structure is interpreted by checking the truthfulness of the first branch (if). If it evaluates to True, program execution continues to the code block inside the statement after which execution skips the rest of the structure. If it evaluates to False, other branches will be evaluated in sequence until one of them is True, or if none of them are, the else branch is executed.
1. Description
2. Examples
Constant is a named literal value. They are used especially when the same literal value is used repeatedly in a program. Named constants are also just in general more practical in code than seemingly arbitrary literal values because its meaning can be derived from its name. Likewise if the value needs to be changed it is much easier if you only need to change it in one place (where it's defined). Python doesn't actually have a way to define "real" constants - they are simply variables. The difference is implied by writing constant names in full upper case. E.g THE_ANSWER = 42.
Control structure is a common name for different programming structures that control the program flow in some way. Within this course this includes conditional structures, loops and exception handling.
Data (engl. data) on ohjelmoinnin asiayhteydessä mitä vaan tietoa, joka ei kuitenkaan yleisesti kata itse ohjelmakoodia. Yleensä datasta puhuttaessa tarkoitetaan yksittäisiä literaaliarvoja, muuttujien sisältämää tietoa tai jostain tietolähteestä (kuten tiedostosta tai verkko-osoitteesta) luettua tai sinne kirjoitettua tietoa. Nyrkkisääntönä voi kuitenkin pitää sitä, että koodi ja data ovat eri asioita, ja koodi käsittelee dataa. (Joissain yhteyksissä koodikin lasketaan dataksi, mutta näihin ei tällä kurssilla syvennytä.)
Data format is the "syntax" of a data file, and it defines how data has been saved to the file. Data format also defines what kind of data can be stored in the file. The basic idea of each data format is to enable the saving of data structures in a program in some format that also makes it possible to load them back in later. A data format can be based on some existing standard (e.g. JSON) but ultimately it's the programmer's responsibility to choose what data is relevant for the program and how to best represent it.
Data structure is a common name for collections that contain multiple values. The purpose of a data structure is to store data that consists of more than one value. There are various ways to make a data structure and each of them convenient means for adding, removing and modifying values. Data structures implement a way to bundle data together. Generally the difficult details involved have been hidden from the programmer.
Choosing data structures that serve the purposes of your program and are easy to handle in your code is essential. The most common structures in Python are list, tuple and dictionary. Another convenient structure is set which doesn't contain duplicate values. In addition to built-in structures, more can be found from the collections module.
On later courses you'll also become familiar with other important structures like trees and graphs.
Debugging is the process of hunting down and fixing programming errors i.e. bugs. There are many ways to track down bugs. One of the more common ones in Python is the error message it shows when a program crashes. Another common method to find errors is the use of debug prints. This means putting additional print function calls in the code temporarily to either see how far the code gets or what kinds of values variables have. Debugging is such an important part of programming that there are even specific debugging tools that have been developed. We don't use them on this course however.
Default value is a value that can be defined for a function parameter. It will be used for that parameter's value if its corresponding argument has not been given in a function call. E.g. in def prompt_length(question, maximum=10): function definition, the maximum parameter has been made optional by giving it the default value of 10.
1. Description
2. Definition
3. Value lookup
4. Modifying dictionaries
Dictionary is a data structure that assigns keys (usually strings) to its values. The advantage of using dictionaries is that descriptively named keys make code that handles the data structure much easier to read. Starting from Python 3.7 dictionary keys and values are guaranteed to be in the order they were added.
In Python docstring is a comment-like entity but it has a special meaning. A docstring is usually delimited with triple quotes (i.e. '''document''' or """document""". If a docstring is placed immediately below a function's def statement (indented!), it becomes the function's documentation that is shown with the help function. Likewise a docstring placed at the very beginning of a code file becomes the module's documentation. A good doctstring describes what a function does, and explains its parameters and return values.
Docstrings should not be used as comments! Outside of the aforementioned places, commenting should be done with actual comments (lines starting with #).
Epätosi (engl. false) on toinen kahdesta mahdollisesta totuusarvosta ja toisen, eli toden, vastakohta. Sitä voidaan pitää lopputuloksena loogisissa ja vertailuoperaatorioissa, jotka eivät pidä paikkansa. Esimerkiksi vertailuoperaatio 5 < 4 ei pidä paikkansa, joten kyseinen operaatio evaluoituu epätodeksi. Pythonissa epätotta merkitään avainsanalla False.
1. Description
2. Examples
Error message is the Python interpreter's way of informing about an exception in a program. The error message contains information about where in the program the exception happened, which line caused the exception, the exception's type (e.g. SyntaxError) and a short verbal description. Error messages are your best friends and reading them is a very integral programming skill. Don't be afraid of them, they are only there to help you find out what's wrong in the code!
Escape in programming terms means interpreting a character in an exceptional way. For instance "n" is just the letter n but "\n" is a newline character. In this example the backslash character \ causes the normal interpretation of the n character to be escaped and replaced by another interpretation. The backslash functions as an escape character. One typical use is including " in a string that's delimited with ": "donkey ear interval is 14\""
Evaluointi (engl. evaluation) tarkoittaa lausekkeen tai muuttujan arvon lopputuloksen määrittämistä. Suoritettaessa lauseet evaluoituvat joksikin tietyksi arvoksi.
Event is a programming cocept that is generally used in the context of interactive applications that run in real time. These applications usually have a main loop that monitors for events. Events include: user clicks with the mouse, user presses a key, a certain amount of time has passed etc. Handler functions can be attached to events, and they will be called whenever the event is detected. This makes programming of interactive programs much easier because there's no need to worry about how actions on the screen are detected when implementing the application itself.
Exception on yleisimpien poikkeusten pääluokka. Kutsumme sitä Pokémon-poikkeukseksi, koska jos sitä käyttää try-except-rakenteessa, except ottaa kiinni kaikki poikkeukset. Tämä ei ole hyvä asia, koska se tekee vikatilanteiden tulkitsemisen vaikeammaksi sekä ohjelman käyttäjälle, että koodarille itselleen – se ottaa nimittäin kiinni myös ohjelmointivirheet, jolloin et saa mitään hyödyllistä tietoa ohjelman kaatuessa.
Execution or running means going through a program or code snippet so that the instructions written within are carried out by the computer. Python interpreter executes code one statement at a time. While this is ongoing the program is "running". Execution ends when there is no more code to run, there's an unrecoverable error or when the program ends itself.
File extension is the part of the file's name that is on the right side of the last period in the name. They are commonly used for indicating file types. Image files for instance often have .png or .jpg as their extension. Python code files usually have .py at the end (e.g. donkeyswings.py).
File handle is a special object that Python uses to refer to an opened file. Most important note is that the handle is not the same as the file's contents - the handle can be used to read the contents, or write to the file. A file handle is obtained with the open function with the file's location (path) and the opening as arguments. E.g. with open("donkey.txt", "r") as somefile: opens donkey.txt inside a with statement (where files usually should be opened), with somefile as the file handle.
Filename is the name of a file that consists of the file's actual name and a file extension. For instance, donkeyswings.py is a complete filename where the given name is donkeyswings and the extension is .py.
Inside code, filenames are always strings.
1. Description
2. Conversions
Floating point number or float is an approximation for decimal numbers used by computers. Computers can't handle real decimal numbers due to their architecture, and that leaves us with floats. Floats can occasionally cause rounding errors - something to keep in mind. Python has a module for handling decimal numbers more accurately, called decimal.
1. Description
2. Examples
The format method of strings is a powerful way in Python to insert values of variables into text that is either printed or saved to a file. Formatting works by defining placeholders in strings (e.g. {:.2f}) for marking spots where the format method arguments will be placed. Example: "Interval between donkey's ears is {:.2f}".format(measurement).
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Function is an independent part of a program that consists of the defining line (with the def statement) and the lines of code that defines the function's behavior. Functions are used to clarify program structure and to reduce redundancy. Functions communicate with each other and the main program through their parameters and return values. Variables (including parameters) defined inside a function cannot be accessed from outside the function. Likewise functions should not read values outside of their own scope.
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2. Examples
Function call is a procedure where the program's execution "jumps" to another location in the code - to the beginning of the function that is being called. When a function is called it is given a varying number of arguments - values that are assigned to parameters defined in corresponding positions in the function definition. A function's execution ends when a return statement is encountered or there are no more lines inside the function's code to execute. When this happens, the program's execution returns to the line where the function was called, and the function call itself is "replaced" by the function's return value.
In short function calls allow one part of the program to utilize another part - e.g. the main program can use a function, or a function can use another function.
1. Description
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Functions are defined with the def statement which specifies the name of the function and the names its parameters. Choosing these is an essential part of writing generally useful functions. The name should describe what the function does accurately but shortly. Parameter names should be chosen so that it's easy to deduce what kinds of values they will take as arguments. The function's code is indented inside the def statement as its own block. A function code can - and often does - include multiple lines. It can also include further indentations (like control structures).
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Generator is a special type of object that works like a list in, for example, a for loop. However, it's not a series of values in memory like a list would be, but a special function that produces values in a lazy way, yielding a new one whenever it is called. Because of this it's not possible to show the "contents" of a generator, and it's not subscribable with indices. Generators are not included in beginner level courses.
1. Description
2. Esimerkit
3. Tilasanakirjat
Globaali muuttuja (engl. global variable) on pääohjelman tasolla esitelty muuttuja, jota muokataan suoraan funktiossa tuomatta sitä funktion nimiavaruuteen parametrin kautta. Globaalien muuttujien käyttö on huonoa ohjelmointityyliä, ja niiden sijaan tietoa kuuluisikin kuljettaa funktioille argumentteina ja ottaa funktiolta vastaan paluuarvoina muutettuja arvoja. Näin tekemällä välttää niin kutsutun globaalin tilan, joka huonontaa koodin ymmärrettävyyttä.
Global scope encompasses all names (variables, functions etc.) that have been defined on the main program level. All names that belong to the global scope can be accessed from anywhere in the program code. However they can only be assigned new values in the main program level. In general functions should only use constants and other functions from the global scope. Main program variables should always be passed to functions through parameters.
A handler function is a function that has been connected to an event so that when the event occurs, the function is called. This often means that the handler is not called from within the same code file or module it was defined in, and instead it works as a callback. Handlers are often related to user interface and game libraries where the program's main loop is running inside the library and monitors events. In this scenario handlers are the actual application's means of implementing their functionality through events. Because the application's writer cannot influence how handlers are called, handler parameters and return values must match the requirements set by the library.
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Hypystä (engl. jump) puhuttaessa tarkoitetaan ohjausrakenteen aiheuttamaa siirtymistä, jonka jälkeen ohjelman suoritus jatkuukin jostain muualta kuin seuraavalta koodiriviltä.
1. Description
2. Naming Conventions
Variables, functions, constants, modules and all kinds of things each have their own 'identifier - the part of the source code that's been assigned to mean that one particular thing. For instace if a programmer defines a variable width with the value 15 the name width can later be used to retrieve the variable's value. So the identifier can be thought of as a contract between the programmer and the Python interpreter about the meaning of a certain word in the code. Identifiers always belong to a namespace.
Indented code lines have blank characters in front of them, either spaces or tabs. The role of indentation in general is to organize code and improve its readability. However in Python indentation is also used as the syntax for separating code blocks from each other - all lines with the same indentation level belong to the same block. On this course we prefer spaces, and the width of one indentation level is 4 spaces. All reasonable text editors can be configured to insert spaces instead of the tab character when the tab key is pressed.
1. Description
2. Example
Index is an integer value that denotes the position of an item in an ordered collection (list, tuple, but also string!). Indices start from zero which makes the last index (collection length - 1). Index can also be thought of as distance from the beginning of the colection. Python supports negative indices where -1 points to the last item, -2 to second to last etc. Using an index to get an item from a collection is called subscription.
1. Description
2. Examples
When the index of a data structure, e.g. list, is used the act itself is called (index) subscription. The subscription is denoted with square braces, e.g. grades[0]. Subscription returns an item. Subscription outside the list causes an IndexError exception, and it's good to keep in mind that the last index of a list is its length - 1 (because indexing starts from zero). Index can also be negative - in this case counting starts from the end so that -1 is the last item of the list.
1. Description
2. Example
An infinite loop is a loop that does not have an end condition - the code inside it gets repeated "infinitely". Infinite loops do have uses in programming but they can also be caused unintentionally by a bug in the code. In Python infinite loops are usually "achieved" only by while loops.
1. Description
2. Examples
Input when used within the context of this course is a text-based command or answer to a question that's been requested from the program's user. It is prompted with the input function and will always be a string. When a program prompts for input the entire program stops until the user has given their input.
1. Description
2. Examples
Interface in general refers to a connection between two things, and in programming it particularly means the way in which two parts of a program are connected to each other. For instance we can talk about the interface of a function which refers to the way in which the function accepts information as parameters and returns information as its return value. Likewise libraries typically have an API (Application Programming Interface) that tells how the library's features are used. Humans are also connected to programs through interfaces, specifically user interfaces.
1. Description
2. Examples
Item or element is an individual value contained within a data structure. The term is most commonly used in the context of lists. In this context, items also have a position, index, that denotes its distance from the beginning of the list. Therefore the index of the first item in a list is 0.
Iteration is a concept related to loops. One iteration of a loop means executing the code inside the loop once.
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2. Examples
Key acts as an index for a dictionary. It can be used to look up a value from the dictionary. Each key corresponds to exactly one value. Keys are typically strings, but they can also be any immutable types like numbers or tuples.
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2. Examples
Keyword argument (kwarg) is used in function and method calls to assign arguments directly to parameter names. This is very often used with the format method: "Hello {name}".format(name="Hagrid"). Another common use case is with functions that have a whole lot of optional arguments and only some of them need to be given. Using keyword arguments can also make the code generally more readable, especially for arguments that are either True or False.
Kirjasto (engl. library) tai moduuli (engl. module) (kuten niitä Pythonissa virallisesti kutsutaan) on valmiiksi kirjoitettua koodia, jolla on oma rajattu tarkoituksensa. Tyypillisesti kirjasto sisältää ainakin nipun aihepiiriinsä kuuluvia funktioita, mutta voi sisältää muutakin (esim. luokkia tai vakioita). Esimerkiksi Turtle on kirjasto, jonka tarkoitus on tarjota helposti käytettäviä piirtofunktioita.
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2. Esimerkit
Kommentti (engl. comment) on kooditiedostossa olevaa tekstiä, joka ohitetaan kun koodia suoritetaan. Kussakin kielessä on oma tapansa sille miten rivi merkitään kommentiksi. Pythonissa se on #- eli risuaitamerkki (engl. hash character), jonka jälkeen riviltä löytyvän tekstin Python-tulkki ohittaa kokonaan. Kommenteilla voi selventää koodin lukijalle (tai itselleen) mitä koodissa tapahtuu. Yleensä kommentit on hyvä laittaa omille riveilleen kommentoitavan koodin yläpuolelle.
Ohjelman ja sen funktioiden toiminta kuvataan yleensä mieluiten dokumenttimerkkijonossa. Kommentteja käytetään enemmänkin välihuomioiden tekemiseen.
Toinen tapa käyttää kommentteja on tilapäisesti kommentoida rivejä pois esimerkiksi vaihtoehtoisen koodin testaamiseksi. Tällöin aiempaa koodia ei tarvitse poistaa – kätevää, jos myöhemmin osoittautuu, että sitä tarvitaan sittenkin.
Ohjelman käyttämät arvot ovat kovakoodattuja (engl. hard coded) silloin, kun ne esiintyvät literaaliarvoina – eli semmoisenaan – ohjelman lähdekoodissa sen sijaan, että ne selvitettäisiin ajonaikaisesti esimerkiksi kysymällä käyttäjältä tai lukemalla tiedostosta.
Käyttöliittymäelementti (engl. UI element, widget) on jokin (yleensä graafiselle) käyttöliittymälle ominainen komponentti, jonka kautta käyttäjän vuorovaikutus ohjelman kanssa on mahdollista. Tällaisia ovat esimerkiksi napit, valikot, liukusäätimet ynnä muut.
Lause (engl. statement) on ohjelmointikielessä nimitys yksittäiselle suoritettavalle asialle, joka on yleensä yksi koodirivi.
Lauseke (engl. expression) tarkoittaa ohjelmoinnissa evaluoitavaa yksikköä. Esimerkiksi 5 + 5 ja "aasi" != "apina" ovat lausekkeita, jotka evaluoituvat arvoiksi 10 ja True. Lauseke yksin ei muuta ohjelman tilaa mitenkään, ellei sillä ole sivuvaikutuksia. Sen sijaan lauseke vaikuttaa osana lausetta.
1. Description
2. Examples
List is an ordered collection of values, and in Python it's a true swiss army knife. A list can contain values of any types, and its size is not limited.
Values inside a list are called items or elements. Each item has its own designated spot inside the list, called index. Indices start from zero! In addition, list is a mutable type. The third material contains a lot of information about lists.
A list can also contain other lists. Such a construct can also be called a two-dimensional list. Of course it's possible to have more than two levels of nested lists, which increases the number of dimensions. These would be called multidimensional lists.
Literal (literal value) is a generic name for any values that are present in the code as such. I.e. the value is not assigned to a variable but has been written into the code itself. For instance in the statements x = 5 and print("donkey"), 5 and "donkey" respectively are literals. The term is used primarily for simple types: numbers, boolean values and strings.
Local variable is a variable that has been defined inside a limited scope, typically - and especially on this course - inside a function (including function parameters). A local variable cannot be accessed from the outside. In addition it gets destroyed when the scope it belongs in stops being relevant - usually when a function call ends.
Loop is a control structure that repeats the instructions contained within it either a certain number of times or until some condition is no longer met. Loops can be used to return program execution to a previous point, and they can also be used for processing large number of values. Python has two kinds of loops: for and while.
Loop Variable is a variable that's introduced in for loop declaration. This variable will receive each value in the sequence (e.g. list) that is being iterated over in the loop. Its value changes on each iteration. A simple example from the material: for animal in animals: where animal is the loop variable. If the sequence contains tuples (or lists), a for loop can also have multiple loop variables: for student, grade in grading:. Loop variables are not inside their own scope and must therefore be distinct from other names inside the same function's scope.
Main program is the part of the code where the real execution of the program starts. As a rule of thumb any statements and control structures that are attached to the left boundary are part of the main program. Main program is usually at the very end of a code file and usually inside if __name__ == "__main__": statement. However do not use this statement in the earlier exercises because then the checker cannot execute your program's main program.
Merkillä (engl. character) tarkoitetaan ohjelmoinnissa yksittäistä datana esiintyvää kirjainta, numeroa, välimerkkiä tai muuta vastaavaa symbolia. Pythonissa merkki edustaa pienintä merkkijonon yksittäistä palasta.
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Merkkijono (engl. string) on tietotyyppi, joka sisältää tekstiä. Sitä käytetään erityisesti käyttäjän kanssa viestimiseen. Merkkijonojen sisältöä voidaan myös tallentaa tiedostoihin. Pythonissa merkkijono merkitään lainaus- tai heittomerkillä (esimerkiksi "aasi" tai 'aasi'). Suosimme ensimmäistä. Merkkijono voidaan merkitä myös kolmella merkillä jolloin se voi olla monirivinen – tätä käytetään erityisesti dokumenttimerkkijonojen (docstring) kanssa. Merkkijono on muuntumaton tietotyyppi – kaikki, mikä näennäisesti muokkaa merkkijonoa, tosiasiassa luo (ja palauttaa) siitä muutetun kopion.
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Method is a function that belongs to an object, i.e. it's one of the object's attributes. Methods are often used by objects to change their own state somehow, or derive another value from themselves. When a method is called it is prefixed with the object that ownds it: choice.lower(). Methods are occasionally called "member functions" as well.
Method Call is a similar process to function calls. As a significant different the target object is defined by prefixing method name with it whereas it would be given as an argument in a function call. In a typical method call an object operates on itself. For instance word.upper() is a method call that operates on the object referred to by the word variable.
Module is basically any Python code file. Although more commonly module is used as a synonym for library. Typically a module contains functions and potentially other (like constants and classes) things that are connected to a certain domain or use case. Large programs are also often split into modules so that each module focuses on one aspect of the program.
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Python objects can be divided into two types: mutable and immutable. Mutable objects can have their values changed during program execution e.g. as the result as a method call. The most common example of a mutable object is a list: hogwarts.append("Hufflepuff") changes a list named hogwarts by adding a new value to it. Any references to this list later in the program will access the contents that now include "Hufflepuff".
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Pythonissa objektit erotellaan muuntuviin ja muuntumattomiin. Muuntumaton (engl. immutable) arvo on sellainen, jonka sisältö ei voi muuttua - kaikki operaatiot jotka näennäisesti muuttavat arvoa tosiasiassa luovat siitä uuden kopion, joka yleensä sijaitsee uudessa muistipaikassa. Esimerkiksi merkkijonot ovat tyypillinen muuntumaton tyyppi Pythonissa. Siksi merkkijonojen kanssa näkee yleensä jotain tällaista: valinta = valinta.lower()
Ohjelmointikielissä on oleellista ymmärtää määrittelyn (engl. definition) ero suorittamiseen. Määrittelemällä luodaan kuvauksia funktioista, muuttujista ja erilaisista tietorakenteista – tavallaan siis kerrotaan ohjelmointikieltä käyttäen, minkälainen jokin edellä mainituista asioista on, tai mitä sen kuuluisi tehdä. Pythonissa määrittelyn ja suorittamisen ero on helpoin ymmärtää funktioiden avulla. Funktiomäärittelyssä funktio vasta luodaan – ikään kuin tehtaalla koottu laite. Funktiota varsinaisesti käytetään – eli sen toiminnallisuus hyödynnetään funktiota varten määriteltyä koodia ajamalla – vasta funktiokutsun yhteydessä. Samaa vertausta käyttäen funktiokutsu vastaa siis sitä hetkeä, kun tehtaalta saapunut laite käynnistetään.
Nimikonflikti syntyy, jos useammalle kuin yhdelle arvolle koitetaan antaa sama nimi. Tällöin tapahtuu niin, että tuoreempi sijoitus jåä voimaan. Tästä seuraa yleensä ohjelman kaatavia virheitä, koska usein arvot ovat eri tyyppiä. Voi jopa käydä niin, että epämääräisesti nimetyn funktion päälle tallennetaan vahingossa saman niminen muuttuja.
Namespace is a group of names (variables, functions, constants etc.) that belong to the same context. For example the names inside a function (inside the function definition code block) form their own namespace: names inside the function are only accessible from within. There's also a global namespace which is the main program's namespace. Using normal import in a program creates a new namespace within that program that is accessible through the module's imported name - the names inside the module form their own namespace. See also: Scope.
Newline (line break, end of line, EOL), the "\n" character is a character that, when printed or written to a file produced a line break. If a string is inspected without printing it e.g. in the console, all line breaks are shown as "\n" characters.
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Nimeämätön vakio tai taikaluku (engl. magic number) on koodissa esiintyvä literaaliarvo, jota ei selitetä millään tavalla. Hyvään ohjelmointityyliin kuuluu taikalukujen välttäminen. Oikea – itsedokumentoiva – tapa on nimetä koodissa esiintyvät vakiot muuttujiin, jolloin niiden muuttaminen onnistuu tarpeen tullen yhdestä paikasta yhdellä muutoksella, ja koodin lukijan on helpompi ymmärtää koodia.
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Näppäimistökeskeytyksellä (engl. keyboard interruption) voi pakottaa jumiin jääneen ohjelman sammumaan. Sen saa aikaan painamalla Ctrl+C sen terminaalin ollessa auki, jossa ohjelma pyörii. Pythonissa näppäimistökeskeytyksen saa käsiteltyä kaappaamalla KeyboardInterrupt-poikkeuksen try-except-rakenteella.
Objekti (engl. object), joskus myös olio, on Pythonissa yleistä terminologiaa. Kutsumme objekteja pääasiassa arvoiksi alkeiskurssilla, mutta Pythonissa kaikkea voi käsitellä objekteina. Tämä tarkoittaa, että mihin tahansa voidaan viitata muuttujilla (esimerkiksi funktion voi sijoittaa muuttujaan). Tämän kurssin puitteissa objekti-termiä käytetään sellaisista arvoista joilla on metodeja.
Objektit nousevat merkittävämpään rooliin alkeista eteenpäin, erityisesti koodissa jossa käytetään luokkia.
Ohjelmointityyli (engl. programming style) on joukko ohjeita tai tapoja, joita ohjelmoija noudattaa koodia kirjoittaessaan. Näihin tapoihin lasketaan muun muassa sisennyksen syvyys, muuttujien ja funktioiden nimeämiskäytännöt, välilyöntien käyttö lauseissa sekä monet muut tyyliseikat. Ohjelmointityylejä on useita erilaisia, ja tällä kurssilla opetetaan noudattamaan tiettyjä tyyliin liittyviä sääntöjä.
Ominaisuus (attribute) liittyy objekteihin siten, että objekteilla voidaan sanoa olevan ominaisuuksia. Tällä kurssilla useimmat näistä ominaisuuksista ovat metodeja, mutta ne voivat olla myös arvoja. Objektin ominaisuutta käsitellään notaatiolla, jossa objektin nimen ja ominaisuuden nimen väliin tulee piste, esim: valinta.lower()-metodikutsussa valinta on objekti ja lower on ominaisuus.
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Opening mode is used for telling Python (and the operating system) how to open a file. A file can be opened for reading or writing. By default, if opening mode is not given, a file will be opened in reading mode "r". There are two writing modes:
• "w", write, which overwrites anything that may have been in the file previously with the new content.
• "a", append, which writes the contents to the end of an existing file instead
Both writing modes create the file if it did not exist previously.
Operand is the fancy name used in mathematics and programming for values that are used in an operation. E.g. 5 + 8 is an addition operation and its operands are 5 and 8. Operands can be thought of as the subjects of operations.
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Operation is a term used for anything carried out by an operator in the code. Mathematical operations are typical examples. An operation consists of an operator and one or two operands. For instance 5 + 5 is an operation.
Operator is a name for symbols that define an operation in mathematics and programming. Operators always appear with at least one operand, but often two. An example of an operator would be + symbol which denotes an addition operation.
An argument in a function call is an optional argument if its corresponding parameter has been given a default value. This means that it's possible to call the function without giving that argument. If there are multiple optional arguments for a function, they are often given using keyword arguments.
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Paikanpidin (engl. placeholder) on yleisesti tilapäinen merkintä, joka on tarkoitus korvata toisella. Tällä kurssilla sitä käytetään lähinnä merkkijonojen muotoilun yhteydessä. Paikanpidin merkkijonon sisällä merkitään aaltosulkeilla ("Hei {}".format(nimi)). Merkkijonojen paikanpitimissä voi olla lisämäärityksiä kuten näytettävien desimaalien lukumäärä ("Aaseilla on keskimäärin {:.2f} jalkaa".format(keskiarvo)). Paikanpitimien tilalle sijoitetaan format-metodikutsun argumentit, normaalisti esiintymisjärjestyksessä. Ne voidaan kuitenkin myös numeroida tai käyttää avainsanoja.
Parameter is a variable defined along with a function. They are variables that are assigned values from arguments when the function is called. In other words when values are transferred in a function call, they are called parameters from the function's point of view. E.g. in def prompt_input(question, error_msg): question and error_msg would be parameters. Parameters can also have a default value that will be used as its value if the matching argument is not given in a function call - this makes the argument optional.
Parametrization means expanding the use cases of a process by turning some of its values into variables. This way the same process can be repeated for multiple sets of values with different results. Mathematical functions are one kind of parametrization: all points represented by the function are produced by changing the value of a variable (e.g. x). In programming parametrization is quite concrete because usually a procedure is turned into a function. The function's parameters then define which values are not fixed and the function will behave differently with different parameters.
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Path is the location of a file or folder on the hard drive. A path can be absolute or relative. Absolute path includes every folder from the target all the to the root (e.g. in Windows the root is the drive letter, like C:) whereas relative only includes folders up to the active folder (i.e. the folder where the program was started in). Path is usually presented in programming languages as a string, and path parts are separated with slashes /. When forming path inside code, it's best to use the join function from the os.path module.
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Poikkeus (engl. exception) on ohjelmointikielessä määritelty virhetilanne. Poikkeuksella on tyyppi (esimerkiksi TypeError), jota voi käyttää poikkeuksen käsittelyssä ohjelman sisällä sekä myös apuna virhetilanteen ratkaisussa. Tyypillisesti poikkeukseen liitetään myös viesti, joka kertoo mistä ongelmassa on kyse. Pythonissa poikkeuksia käsitellään try-except-rakenteilla.
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Poikkeusten käsittely (engl. exception handling) on ohjelmointikieleen sisäänrakennettu keino ohjelmoijalle reagoida poikkeuksiin. Pythonissa poikkeusten käsittely onnistuu try-except-rakenteella, jossa sekä try: että except: aloittavat omat lohkonsa; try-lohkon alle kirjoitetaan se koodi, joka mahdollisesti aiheuttaa jonkun tietyn poikkeuksen ja except-lohkon alle taas se koodi, joka suoritetaan siinä tapauksessa, että kyseinen poikkeus tapahtuu. Joissain muissa ohjelmointikielissä except-avainsanan sijaan käytetään avainsanaa catch, minkä takia yleisesti puhutaan poikkeusten kiinni ottamisesta.
Precedence defines the execution order of instructions or operations on a line of code. Operations of different type have different precedence in execution order. These can be found from the link below. Operations with same precedence are executed from left to right. Like in mathematics, the order can be changed by using parentheses.
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Printing is somewhat different in programming context - although not really that far removed - from combining paper and ink to pages. In context of computer programs it usually means producing text on the screen, especially to a terminal. Python has a function for this purpose: print(...) that prints its argument(s) to the terminal.
Programming problem is the goal of a programming task. It is therefore some sort of a need that has been recognized and a program is coded to fulfill that need. The need can be e.g. automatization of a task, creating a web site or just making a fun game.
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Interactive Python interpreter or Python console as we like to call it is a program that executes Python code lines as they are written into it. It shows the return value of the line if any exists (e.g. the result of a mathematical operation). On this course we use IPython instead of the vanilla Python console. After installation you can start IPython by typing ipython to the terminal.
Python interpretetr is a program that transforms Python code into instructions to the computer's processor. It's responsible for executing both code files and individual lines in the Python console. The word can also be used to mean Python console though, so be careful.
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Recursion is a common programming term that refers to a function calling itself. Recursion is a function-based way to create repetition in the code where the function gives itself new arguments and handles its own return values. Recursion is handy e.g. when navigating tree-like structures - one "branch" is handled at a time, and then recursion is used to handle branches branching out from that branch, and so on. Recursion is not very widely used in Python. One reason is the recursion depth limit which restricts how many times a function can call itself.
Referring is the method in which a variable is connected to its value. The target of the reference is the computer's memory and the variable itself - under the hood - contains an address where from memory the value can be found.
Relative path is an operating system concept that indicates the path to a file or folder from the current folder. Relative paths do not care what kind of a garden maze of folders exists between the disk drive root and the current path. For this reason relative paths are usually used to refer to a program's own sub folders. This allows the program to be moved to another location without updating any paths in the code.
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Return is a process that happens when a function's execution ends. Typically the value(s) returned by the function are defined inside the function with a return statement. In the code that calls the function, the return value will replace the function call and can therefore be assigned to a variable or passed on to another function.
Return value is the value (or values) that a function returns when its execution ends - the function's result. Functions in Python can have multiple return values. When reading code you can regard return value as something that will replace the function call when the function execution has ended. A return value is defined inside a function with the return statement. E.g. in return True there is one return value: the literal boolean value True.
Sapluuna (engl. template) on muotti esimerkiksi tekstille, joka käyttäjälle halutaan näyttää, mutta joka ei semmoisenaan ole vielä valmis. Sapluunasta siis puuttuu tietoa, joka on tarkoitus saada sapluunan paikanpitimien tilalle.
Kurssilla yleisin sapluuna on merkkijono, jossa on paikanpitimiä format-metodia varten.
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Scope is a concept related to the visibility of names (variable, function etc.) in certain parts of the program. For instance within a function block any names defined inside the function can be used because they belong to the same scope. Other functions cannot access these names because they belong to a different scope. Names in the global (main program) scope can be accessed from anywhere in the code.
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Separator is a term related to strings and text files. It means a specific character that is meant for indicating a split inside a string when it is read into the program. For instance, if a string contains values that will be parsed into a list, the separator is the character than indicates where one part ends and the next one begins. The split method is often used in these situations - the method can use a specific separator to split a string into a list.
A sequence is any value in Python that is a series of things - for instance, string, list and tuple are all sequences.
Matematiikasta tuttu sidontajärjestys (engl. precedence) määrittää sen, missä järjestyksessä lausekkeen operaatiot suoritetaan.
lopputulos = 10 + 2 * (2 + 3)

Yllä olevan koodin lopputulos on 20, sillä ensin lasketaan yhteen luvut 2 ja 3, joiden summa kerrotaan kahdella, ja johon lopuksi lasketaan vielä yhteen luku 10. Esimerkissä korkein presedenssi on siis sulkeilla, toisiksi korkein kertolaskulla ja matalin yhteenlaskulla.
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Slicing is the act of taking a new sub-sequence out from an existing sequence (usually list, but sometimes also string). The result of slicing is a value with the same type that's a copy of the selected part in the original sequence. The selection is done by choosing start and end indices. Both are optional. A slice is written as follows: page = collection[5:10] - this would make a slice including indices 5...9. The number on the right side of the colon in a slice is the first index that is not included in the result!
Slicing never causes an IndexError.
Solution model is an abstract construct developed by a programmer regarding how the solution to a programming problem works. It's not code yet, but it should be explicit and dividable into distinctive steps so that it can be turned into a program. Solution models can be sketched inside one's mind, by using paper and by trying this out in the Python console.
Source code or code means text that has been written with a programming language.
State, as the name suggets, referes to the program's current state. In practice state covers everything belonging to the program's state space like variable values, data in files, and where the code execution is currently at. A guaranteed way to make spaghetti code that's beyond repair is to use the global state - a crime that's perpetrated by functions that use global variables.
Later, on courses that go more formally into programming concepts, you'll learn of things like state machines, as well as stateless and stateful programs.
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Stub function is a function that's been defined properly with all the parameters etc. but has no content in it. They are typically put into the program code when planning its overall structure. Doing so allows the functions to be called elsewhere in the code while the function isn't fully implemented yet. The contents of a stub function usually come down to just pass, an informative print, or returning some placeholder default value. In larger projects stub functions sometimes are set to raise a NotImplementedError exception which makes it easy to locate the function that's not ready yet.
Syntaksi (engl. syntax) on koodin kielioppi. Esimerkiksi Pythonin syntaksi määrittää, millainen teksti on tulkittavissa Python-koodiksi. Jos teksti ei noudata koodin syntaksia, sitä ei voida suorittaa. Syntaksi antaa myös koodaajalle tietoa siitä, missä muodossa halutunlainen ohje tulee antaa.
Syntax error is an exception that happens when the Python interpreter inspects a code file before executing it and notices something broken in there, i.e. code that is written incorrectly. A code with syntax errors is not run at all.
One common syntax error is unbalanced parentheses. This results in a strange error message in the sense that Python reports the next line as the cause of the error. Remember to check previous lines as well when you receive strange syntax errors!
Takaisinkutsu (engl. callback) on yleinen ohjelmoinnissa käytetty menetelmä, jossa funktio ottaa parametrin kautta vastaan funktion kutsuttavakseen heti (synkroniset takaisinkutsut) tai joskus tulevaisuudessa (asynkroniset takaisinkutsut). Nimensä menetelmä on saanut soittopyynnöstä: kutsuttavaa funktiota, jolle jokin funktio välitetään argumenttina, ”pyydetään” kutsumaan tätä annettua funktiota. Pythonissa listojen sort()-metodin key-parametri on esimerkki callback-funktioiden käytöstä. Usein käyttöliittymiä toteutettaessa käyttöliittymäelementteihin kytketään callback-funktioita.
Terminal, command line, command prompt and shell' are different names to the text based interace of an operating system. It is used for text-based operating system commands and for running terminal programs. On this course we mostly move around with cd (change directory) and use ipython command to run code files and start the Python console.
• In Windows you can open the terminal by typing cmd to the start menu search
• In Mac OS X you can start the terminal by typing terminal to Finder
• In Linux you can open the terminal from the desktop by pressing Ctrl + Alt + T or by typing terminal to the search
Testaamalla eli kokeilemalla (engl. test) selvitetään, toimivatko hartaasti näppäillyt koodirivit halutulla tavalla. Testejä suorittamalla siis etsitään koodista mahdollisia ohjelmointivirheitä. Ohjelmien testaaminen on jopa niin olennaista, että joidenkin alan työntekijöiden tehtävänä on ainoastaan automatisoitujen testien ohjelmointi. Lovelace-järjestelmän tarkistimet testaavat järjestelmään lähetetyt koodit.
Generally text file is any file that can be read with a text editor. In this course's context we use text file to refer to files that are handled as text inside Python. We do this to separate them from code files that are run with Python. Text files are used in this course to store data between runs of the program.
Tosi (engl. true) on toinen kahdesta mahdollisesta totuusarvosta ja toisen, eli epätoden, vastakohta. Sitä voidaan pitää lopputuloksena loogisissa ja vertailuoperaatorioissa, jotka pitävät paikkansa. Esimerkiksi vertailuoperaatio 5 > 4 pitää paikkansa, joten kyseinen operaatio evaluoituu todeksi. Pythonissa totta merkitään avainsanalla True.
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Traceback is the process of tracing an error back to its source. When an exception occurs the Python interpreter prints an error message that includes a traceback. It's presented as a stack of function calls where the last one is the funtion where the exception occurred. They are also called stacktrace for this reason. For example if the main program calls the funcion f which in turn calls function g where the exception occurs, the stack would be
main programfg.
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Tuple is a co-called frozen list. It's an ordered collection of values like a list but it's an immutable object. A tuple can't be changed. They can only be created, and read. Usually a tuple is delimited with normal braces: "#!python3 (1, 2, 3) but actually this is a tuple even without them: 1, 2, 3.
Unlike lists, tuples can be used as dictionary keys.
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Type conversion (also type casting and type coercion) means changing the type of a variable or literal value to another one. In Python this is commonly done when a number is requested from the user and it is returned as a string. In practice this can be done with e.g. int("123") or float("3.14"). In some cases Python performs type conversion automatically, usually when mathing with floats and integers.
Tyylisäännöt ovat kokoelma suosituksia, joiden mukaan koodia tulisi kirjoittaa. Kullakin kielellä on yleensä omansa. Tyylisääntöjen rikkominen ei varsinaisesti riko ohjelmaa, mutta tyylisääntöjen mukainen koodi on miellyttävämpää lukea ja usein tästä johtuen myös helpompi korjata. Tällä kurssilla seurataan Pythonin virallista tyylistandardia erityisesti tekstikenttätehtävissä. Myös tiedostotehtävissä on koodin laadun tarkistus, jossa käytetään PyLint-ohjelmaa.
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Tyyppi (engl. type) on arvon ominaisuus – jokainen arvo edustaa aina jotain tiettyä tyyppiä. Tyypin tarkoitus on siis kertoa, minkälaisesta arvosta on kyse. Käytännössä tästä seuraa myös se, mitä operaatioita arvoilla voi tehdä, ja mitä metodeja niiltä löytyy. Funktiot on myös miltei aina toteutettu siten, että niille syötettävien argumenttien täytyy olla tietyntyyppisiä, jotta funktio voisi toimia. Tyypit ovat yksi ohjelmoinnin keskeisimmistä käsitteistä.
Pythonissa arvojen sopiminen koodista löytyviin operaatioihin tarkistetaan tilannekohtaisesti näiden arvon ominaisuuksien perusteella – ei siis suoraan itse tyyppiä tarkastamalla. Esimerkiksi useimmissa tapauksissa kokonaisluku ja liukuluku kelpaavat molemmat, mutta on myös tapauksia, joissa näin ei ole (esimerkiksi merkkijonoa ei voi kertoa liukuluvulla).
Tällä kurssilla tyypillisiä tyyppejä ovat kokonaisluku (int), liukuluku (float), merkkijono (str), lista (list), totuusarvo (bool) ja monikko (tuple). Myös funktioilla on oma tyyppinsä!
User Interface (UI) is the interface between a program and its user (typically human). In a simple text based UI input function calls are used to prompt things from the user and print calls can be used to display instructions and results.
Many programs intended for end users (consumers) typically offer a graphical user interface (GUI). These typically involve icons, popup menus and other elements that can be poked with by mouse or touch screen. On this course we will take a very shallow stab at graphical user interfaces in the final project.
A simplified way to describe variable is to think of it as an information storage - it contains something. This expression is often used in speech even though it's not entirely accurate. The more accurate description is that a Python variable is a reference to a value. It's a connection between the variable's human-readable name and a value that's stored in the computer's memory. So the variable in fact doesn't contain the value, it just contains information about where it is.
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The break keyword is a special instruction that is used in loops. It interrupts the loop's execution immediately, and code execution continues from the first line after the loop. If the loop had an else branch, it is not entered.
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continue is the other keyword related to loops (the first one being break). Unlike break which interrupts the entire loop, continue only interrupts the current iteration - execution continues from the next iteration. Note that this keyword is only needed in situations where part of the iteration is to be skipped. There's no need to put continue to the end of the loop iteration.
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enumerate is builtin function that produces a generator-like object in Python. Its primary use is in for loops when the code needs to access the items' indices in addition to the items themselves. The enumerate object produces tuples where the first item is the original item's index and the second item is the original item itself. Use example: for i, character in enumerate(moomin_valley):.
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In Python for is one of the two loop types. It's designated for iterating through data structures. It is used especially with lists. In general, for loops are used when it's possible to determine in advance how many iterations the loop must do. In addition to iterating through structures, for loop is therefore used for doing a certain number of iterations (e.g. 10 iterations). For loop declarion looks like for item in collection: where item would be the name of the loop variable, and collection would be the data structure that is being iterated over.
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In Python modules are "activated" by import statements. In normal use (e.g. import math) the statement makes a new namespace accessible through the module name. Functions from the imported module can be accessed through its name. It's also possible to directly import some specific names from a module with a from-import statement: from math import ceil. Modules can also be renamed on import: import math as m.
1. Description
2. Esimerkit
Silmukoista while pohjautuu toistoon ehdon tarkastelun kautta - silmukan sisällä olevaa koodilohkoa suoritetaan niin kauan kuin silmukalle annettu ehto on tosi. Ehto määritetään samalla tavalla kuin ehtolauseissa, esim: while summa < 21. While-silmukat soveltuvat parhaiten sellaisiin tilanteisiin, joissa ei voida etukäteen selvittää montako toistoa tarvitaan - erityisesti syötteiden kysyminen käyttäjältä on tällainen tilanne.
1. Description
2. Examples
In Python with is a somewhat exception keyword in that it's not a control flow structure or definition of a new thing. On this course it's primarily used when opening files, e.g. with open("donkey.txt") as somefile:. All read or write operations on the file are carried out inside the with statement. When the with statement ends, Python automatically takes care of closing files opened in the with statement.