1. A
    1. Absolute Path
    2. Ajonaikainen
    3. Alustaminen
      variables values
    4. Argumentti
      values functions
    5. Arvo
    6. Assignment
      variables values
    7. Assignment Operator
      variables values operators
    8. Attribute
    9. Attribuutti
    10. Avainsana
    11. Aliohjelma
  2. B
    1. Boolean
      control flow
    2. Boolean Operator
      control flow operators
    3. Boolen operaattori
      Boolean Operator
    4. Branch
      try structures conditional structures
    5. Bug
      problem solving
    6. Bugi
    7. Builtin Function
    8. Block
      Code Block
    9. break
      loops keywords
  3. C
    1. Callback
    2. Carriage Return
      escaping strings files windows
    3. Code Block
      control flow functions
    4. Code File
    5. Command Line Argument
    6. Comparison Operator
      control flow operators
    7. Comparison Value
    8. Condition
      control flow
    9. Conditional Statement
      control flow
    10. Conditional Structure
      conditional structures control flow
    11. Constant
      variables values
    12. Control Structure
      try structures loops conditional structures
    13. Call
      Function Call
    14. Ctrl + C
    15. Code
      Source Code
    16. Callback
    17. Command Prompt
    18. continue
      loops keywords
  4. D
    1. Data
    2. Data Format
      strings files
    3. Data Structure
      dictionaries concepts lists
    4. Debugging
    5. Default Value
      values functions parameters
    6. Dictionary
      data structures
    7. Docstring
  5. E
    1. Epätosi
    2. Error Message
      problem solving
    3. Escape
    4. Evaluointi
      expressions values
    5. Event
    6. Exception
      try structures problem solving
    7. Exception class
      exceptions control flow
    8. Execution
      expressions concepts
    9. Element
    10. enumerate
      lists loops
  6. F
    1. False
    2. File Extension
    3. File Handle
      objects files
    4. Filename
      strings files
    5. Float
      values types
    6. Format
      strings printing
    7. Formatting
    8. Function
    9. Function Call
      functions statements
    10. Function Definition
    11. f string
    12. for
  7. G
    1. Generator
      objects loops
    2. Globaali muuttuja
      variables values
    3. Global Scope
  8. H
    1. Handle
      File Handle
    2. Handler
      functions concepts
    3. Hyppy
      control flow
    4. Hardkoodaus
  9. I
    1. if statement
      Conditional Statement
    2. if structure
      Conditional Structure
    3. Identifier
      variables functions
    4. Indentation
    5. Index
      values lists
    6. Index Subscription
      values lists
    7. Infinite Loop
    8. Input
      strings concepts
    9. Interface
      modules functions concepts
    10. Item
      values lists
    11. Iteration
    12. import
  10. K
    1. Key
      dictionaries values
    2. Keyword Argument
    3. Kirjasto
    4. Kommentti
      debugging documentation
    5. Kovakoodaus
    6. Käyttöliittymäelementti
    7. KeyboardInterrupt
  11. L
    1. Lause
    2. Lauseke
    3. List
    4. Literal
    5. Local Variable
    6. Loop
      control flow
    7. Loop Variable
      variables loops
  12. M
    1. Main Program
    2. Merkki
    3. Merkkijono
      values types
    4. Method
      functions objects
    5. Member Function
    6. Method Call
      expressions objects
    7. Module
    8. Mutable
      values concepts lists
    9. Muuntumaton
      values strings concepts
    10. Määrittely
  13. N
    1. Name Conflict
    2. Namespace
      modules functions concepts
    3. Newline
      strings files
    4. Nimeämätön vakio
      values constants
    5. Näppäimistökeskeytys
  14. O
    1. Objekti
    2. Olio
    3. Ohjelmointityyli
    4. Ominaisuus
    5. Opening Mode
    6. Operand
    7. Operation
    8. Operator
    9. Optional Argument
      values functions parameters
  15. P
    1. Parameter
    2. Parametrization
    3. Path
    4. Placeholder
      strings printing
    5. Poikkeusten käsittely
      control flow exceptions
    6. Precedence
    7. Precedence
      expressions concepts
    8. Presedenssi
    9. Printing
      strings concepts
    10. Programming Problem
      problem solving
    11. Python Console
    12. Python Interpreter
  16. R
    1. Running
    2. Recursion
      functions concepts
    3. Referring
      variables values objects
    4. Relative Path
    5. Return
      values functions
    6. Return Value
  17. S
    1. Silmukka
    2. Suoritusjärjestys
    3. Sapluuna
      strings concepts
    4. Scope
      concepts blocks
    5. Separator
      strings files lists input
    6. Sequence
      data structures concepts loops
    7. Slicing
    8. Solution Model
      problem solving
    9. Source Code
    10. State
    11. Stub
      problem solving functions
    12. Syntax
    13. Syntax Error
    14. Shell
    15. Stacktrace
  18. T
    1. Taikaluku
      Nimeämätön vakio
    2. try-rakenne
      Poikkeusten käsittely
    3. Takaisinkutsu
    4. Terminal
    5. Testaaminen
      problem solving concepts
    6. Text File
    7. Tosi
    8. True
    9. Traceback
      problem solving
    10. Tuple
      data structures lists
    11. Type Conversion
      values functions types
    12. Tyylisääntö
    13. Tyyppi
      values concepts
  19. U
    1. User Interface
  20. V
    1. Variable
      values concepts
  21. W
    1. while
    2. with
Completed: / exercises


In electron spectroscopy matter is examined by radiating it with a bright light and measuring the kinetic energy of electrons that come off it. When the photonic energy of light and kinetic energy of the electrons are known, they can be used to derive the amount of force that was required to break off the electrons. This provides valuable information about the matter's electron structure, and its chemical and physical properties. This phenomenon where photons break off electrons is called photoionization, and the broken off electrons are called photoelectrons.
In this course project you'll learn how to read data into a program and how to perform small operations on the data, and how to plot data using Python libraries. Your task is to write a program for analyzing the photoionization spectrum of argon. For this purpose we have provided you with simulated data where argon atoms have been ionized and the kinetic energy of broken off electrons has been measured.

About Libraries

This project requires you to use two third party libraries: numpy and matplotlib. There are multiple ways to install them. Windows installers can be found for both, and you can also install them using pip. There are also various full stack installers available in the internet (full stack means they install Python along with a bunch of libraries, usually replacing your "generic" Python installation). Please write a comment in your code if you use any such full stack installer because they might contain different versions of the libraries than those available generally.
You'll also need our small graphical user interface library - more about it below.

Specific Requirements

The measurement has been performed multiple times, and each measurement session has been recorded into a different, numbered file. The file names are in the format measurement_i.txt. Each file contains rows of data with two floating point numbers. The first number on each line is the binding energy of electrons, derived from the measured kinetic energy (unit: electronvolt); the second number is the corresponding intensity (no specific unit; this described the amount of electrons measured with this particular binding energy). In each measurement file, the first column contains the same uniformly distributed binding energy values. Your program should add together the intensity values from each file. The purpose is to eliminate noise from the measurements.
Due to the measuring equipment, the spectrum has a linear background. Aside from the obvious peaks it looks like a downward sloping line. The background signal that causes the sloping should be removed before analyzing the spectrum. This can be done by choosing two points from the spectrum and fitting a line between these points. After this, at each data point, values obtained from this line are subtracted from the measured intensity values.
When analyzing the spectrum our primary interest are the two rather obvious peaks in intensity; in particular, their relative intensity. The intensity of each peak is obtained by computing their area by obtaining its integral. This can obtained by using the trapezoidal rule to estimate the integral. According to theory the first peak should have approximately double the intensity of the second one.
Your program needs to have the following features:
  1. Your program has a graphical user interface with all the features available for the user.
  2. Load data: loads data from a user-specified location and reads it into program memory in a format that is suitable for processing. Should return one list for each column in the data. The first list should contain measured kinetic energy values (measurement points) and the second one the sums of all measurements for each row.
  3. Plot data: this plots the current data (the user is prompted to load the data first if it hasn't been loaded yet). You can plot the data using matplotlib, but it must be plotted inside the application window - do not use pyplot. The figure should look like the one below.
  4. Remove linear background: removes the linear background from the data as described above. The user selects two points from the figure, and a line is fitted between these points. The line is then subtracted from the data. If there's no data in the program memory yet, the user is given an error message about it.
  5. Calculate intensities: The intensity of peaks can be calculated. This is done with the trapz function from numpy. The use selects the interval by clicking on the figure. The result is printed somewhere inside the window. If there's no data in the program memory yet, the user is given an error message about it.
  6. Save figure: this feature allows the user to save an image of the current plot. The user uses a separate dialog for select a filename and destination for saving the figure. matplotlib provides you with the necessary features to do this.
You should name the axes in your figure with appropriate names. There are tools for doing this in matplotlib.
Figure where the noise is centered around a downward slanted line (from intensity 30 to 20, approximately). There two spikes in the data, the first roughly double the height of the second one
Example plot of the data



We've provided a library that is built on top of TkInter, and offers a heavily simplified interface to some of its features through functions. The library's docstrings describe how to use it. The lirary's main program also has a short example of how to make a simple interface.

User Interface Libraries 101

In user interface programming the main loop is usually contained inside the library being used. All of the user's actions are connected to handler functions. For instance, when the user presses a button, the handler function attached to that button is called, and it does Something. The program doesn't proceed as linearly as we've used to. User interfaces consist of components or elements that are also often called widgets. These can be simple, like buttons, or more complex like an entire file opening dialog - one you can see in many programs.
Typically an interface is created by choosing what components to put in there. While doing so, their attributes and handler functions are also defined. Rest of the implementation comes down to creating these handler functions and bunch of utility functions (that are used by the handlers).
One special characteristic is that functions are called kind of externally from the user interface library, and therefore we cannot control what arguments they are given. It's not possible to transmit the program's state in function arguments - another way to share it needs to be devised. A good choice in the context of this project is to make a dictionary that has keys for things like loaded data and data points selected by the user. If the dictionary is defined in the main program scope it can be handled in all functions, thanks to its mutability. This way any function can change the program state without having been given it as an argument.

Return Box

Deadline: 2024-08-31 23:59
You can return your project here. If you're returning multiple files, you can either zip them or use Ctrl when selecting files to upload many at once.
Jos pakkaat tiedostoja, pakkaa ne zip-muodossa!

Allowed filenames: *.py, *.zip

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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
  2. Kurssin avainsanat
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.
  1. Description
  2. Examples
Exception is a scenario in programming where the program cannot proceed as instructed. Exceptions have a type (e.g. TypeError) that can be used in handling the exception within the program. Type can also be useful when trying to solve the issue if it is not intended. In most cases exceptions also come with a message that gives more details about what caused the issue. In Python exceptions are handled with try-except structures.
Exception is the base class of most common exceptions. We also call it the Pokémon exception because if you use it in a try-except structure it will catch all the exceptions. In most cases this is not a good thing. It makes interpreting problem situations more difficult for both the user, and you, the developer. The latter is due to the fact that it will also catch any mistakes you made in your code, and you won't get any useful information when the program isn't behaving correctly.
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
  3. Choosing parameters
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).
Note: format is an older way for general string formatting. Using f strings is a more modern way. However, there are still uses for the good old format method too.
  1. Description
  2. Examples
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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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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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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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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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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.
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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.
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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Placeholder is by general definition a way to mark a spot that will be replaced by something else later. In this course they are primarily used with string formatting. A placeholder within an formatting string is marked with curly braces (f"Hi {name}"). Placeholders in strings can also contain additional formatting specifiers like setting the number of decimals to show (f"Donkeys have {average:.2f} legs on average"). When a placeholder is resolved, it is replaced by the value of the variable or statement inside the curly braces.
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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.
Precedence, of math fame, defines in which order various operations in a statement are resolved.
result = 10 + 2 * (2 + 3)
The result of this statement is 20 because the sum of 2 and 3 is resolved first, followed by multiplying the result by 2, and finally adding the multiplication result to 10. In this example the highest precedence is held by the operation in braces, followed by multiplication, and then finally addition.
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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.
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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.
Syntax is the grammar of code. It defines what kind of text counts as valid Python. If code doesn't conform to the correct syntax, it cannot be executed. Syntax also informs a programmer about the correct formatting for each stement in the programming language.
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):.
f(ormat) string is a special string that is used for inserting values from variables or simple clauses inside a piece of text. This is also called string interpolation in programming terminology. This kind of a string is marked by prefixing it with a lowercase f. You can include placeholders inside the string by using curly braces, and writing variable names or clauses inside them.
Example: f"Interval between donkey's ears is {measurement:.2f} inches" (assuming that a variable named measurement has been definied previously)
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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.
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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.
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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.