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‎README.md

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# Python programming tutorial
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This is a Python 3 programming tutorial for beginners. If you have never
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programmed before click [here](basics/what-is-programming.md) to find
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out what programming is like and get started.
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This is a concise Python 3 programming tutorial for people who think
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that reading is boring. I try to show everything with simple code
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examples; there are no long and complicated explanations with fancy
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words. If you have never programmed before click
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[here](basics/what-is-programming.md) to find out what programming is
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like and get started.
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This tutorial is aimed at people with no programming experience at all
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or very little programming experience. If you have programmed a lot in
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the past using some other language you may want to read [the official
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tutorial](https://docs.python.org/3/tutorial/) instead.
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You can use Python 3.2 or any newer Python with this tutorial. Don't use
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Python 2. If you write a Python 2 program now someone will need to port
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it to Python 3 later, so it's best to just write Python 3 to begin with.
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Python 3 code will work just fine in Python 4, so you don't need to
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worry about that.
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You can use Python 3.3 or any newer Python with this tutorial. **Don't
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use Python 2.** If you write a Python 2 program now someone will need to
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convert it to Python 3 later, so it's best to just write Python 3 to
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begin with. Python 3 code will work just fine in Python 4, so you don't
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need to worry about that. Python 2 also has horrible
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[Unicode](http://www.unicode.org/standard/WhatIsUnicode.html) problems,
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so it's difficult to write Python 2 code that works correctly with
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non-English characters (like π and ♫).
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## List of contents
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‎TODO.md

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- "What the heck is this?" section for stuff i haven't talked about
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- regexes
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- add a screenshot about geany's running settings to
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basics/editor-setup.md
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***
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If you have trouble with this tutorial please [tell me about

‎advanced/datatypes.md

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We can also convert anything [iterable](../basics/loops.md#summary) to a
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set [by calling the
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class](../basics/classes.md#why-should-I-use-custom-classes-in-my-projects).
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class](../basics/classes.md#what-are-classes).
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```python
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>>> set('hello')

‎basics/classes.md

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# Defining and using custom classes in Python
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# Defining and using custom classes
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When I was getting started in Python I learned to make classes for
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tkinter GUI's before I understood how they work. Everything I did with
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classes worked, but I didn't understand how. Hopefully you'll first
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learn to understand classes, and then learn to use them.
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## Why should I use custom classes in my projects?
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## What are classes?
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Python comes with a lot of classes that you are already familiar with.
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Python comes with many classes that we know already.
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```python
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>>> str
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>>>
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```
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Let's say you make a program that processes data about websites. With a
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custom class, you're not limited to `str`, `int` and other classes
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Python comes with. Instead you can define a Website class, and make
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Websites and process information about websites directly. Defining your
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own object types like this is called **object-orientated programming**.
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Let's say that we make a program that processes data about websites.
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With a custom class, we're not limited to `str`, `int` and other classes
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Python comes with. Instead we can define a Website class, and make
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Websites and process information about websites directly. Defining our
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own types like this is called **object-orientated programming**.
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## First class
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>>>
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```
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The `pass` is needed here, just like [when defining functions that do
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nothing](defining-functions.md#first-functions).
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Note that I named the class `Website`, not `website`. This way we know
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that it's a class. Built-in classes use lowercase names (like `str`
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instead of `Str`) because they are faster to type, but use CapsWord

‎basics/defining-functions.md

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that prints text in a box. We can write the code for printing the
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box once, and then use it multiple times anywhere in the program.
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Dividing a long program into simple functions also makes the code
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easier to work with. If there's a problem with the code we can
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test the functions one by one and find the problem easily.
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[Dividing a long program into simple functions](larger-program.md) also
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makes the code easier to work with. If there's a problem with the code
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we can test the functions one by one and find the problem easily.
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## First functions
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>>>
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```
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Seems to be working so far, we have a function. Actually it's just
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a value that is assigned to a variable called `do_nothing`. Let's see
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what happens if we call it.
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Seems to be working so far, we have a function. It's just a value that
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is assigned to a variable called `do_nothing`. You can ignore the
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`0xblablabla` stuff for now.
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The `pass` is needed here because without it, Python doesn't know when
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the function ends and it gives us a syntax error. We don't need the
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`pass` when our functions contain something else.
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Let's see what happens if we call our function.
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```python
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>>> do_nothing()
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Fortunately, Python will tell us if something's wrong.
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```python
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>>> foo = 1
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>>> def bar():
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... foo += 1
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>>> thing = 1
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>>> def stuff():
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... thing += 1
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...
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>>> bar()
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>>> stuff()
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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File "<stdin>", line 2, in bar
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UnboundLocalError: local variable 'foo' referenced before assignment
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File "<stdin>", line 2, in stuff
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UnboundLocalError: local variable 'thing' referenced before assignment
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>>>
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```
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print(character * len(message))
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```
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Then we could change our existing code to always call `print_box` with
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a star as the second argument:
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Then we could change our code to always call `print_box` with a star as
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the second argument:
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```python
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print_box("Hello World", "*")
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## Output
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The built-in input function [returns a value](using-functions.md#return-values).
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Can our function return a value also?
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Can our function return a value too?
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```python
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>>> def times_two(x):
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... return x * 2
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>>> def times_two(thing):
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... return thing * 2
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...
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>>> times_two(3)
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## Return or print?
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There's two ways to output information from functions. They can print
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There are two ways to output information from functions. They can print
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something or they can return something. So, should we print or return?
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Most of the time **returning makes functions much easier to use**. Think
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>>>
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```
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## Common problems
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Functions are easy to understand, but you need to pay attention to how
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you're calling them. Note that `some_function` and `some_function()` do
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two completely different things.
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```python
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>>> def say_hi():
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... print("howdy hi")
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...
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>>> say_hi # just checking what it is, doesn't run anything
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<function say_hi at 0x7f997d2a8510>
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>>> say_hi() # this runs it
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howdy hi
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>>>
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```
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Typing `say_hi` just gives us the value of the `say_hi` variable, which
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is the function we defined. But `say_hi()` **calls** that function, so
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it runs and gives us a return value. The return value is None so the
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`>>>` prompt [doesn't show it](#variables.md#none).
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But we know that the print function shows None, so what happens if we
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wrap the whole thing in `print()`?
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```python
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>>> print(say_hi) # prints the function, just like plain say_hi
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<function say_hi at 0x7fd913f58488>
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>>> print(say_hi()) # runs the function and then prints the return value
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howdy hi
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None
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>>>
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```
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The `print(say_hi())` thing looks a bit weird at first, but it's easy to
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understand. There's a print insnde `say_hi` and there's also the print
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we just wrote, so two things are printed. Python first ran `say_hi()`,
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and it returned None so Python did `print(None)`. Adding an extra
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`print()` around a function call is actually a common mistake, and I
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have helped many people with this problem.
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## Examples
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Ask yes/no questions.
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while True:
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if answer in correct_options:
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return answer # returning ends the function
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return answer
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print(error_message)
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function does. Returning also ends the function immediately.
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- Return a value instead of printing it if you need to do something with
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it after calling the function.
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- Remember that `thing`, `thing()`, `print(thing)` and `print(thing())`
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do different things.
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## Exercises
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‎basics/getting-started.md

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## Comments
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We can also type a `#` and then whatever we want after that. These bits
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of text are known as **comments**, and we'll find uses for them later.
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**Comments are text that does nothing.** They can be created by typing a
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`#` and then some text after it, and they are useful when our code would
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be hard to understand without them.
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```python
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>>> 1 + 2 # can you guess what the result is?
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Again, I put a space after the `#` and multiple spaces before it just to
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make things easier to read.
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If we write comment on a line with no code on it, the prompt changes
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If we write a comment on a line with no code on it, the prompt changes
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from `>>>` to `...`. To be honest, I have no idea why it does that and I
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think it would be better if it would just stay as `>>>`. The prompt goes
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back to `>>>` when we press Enter again.
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>>>
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```
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## Strings
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Strings are small pieces of text that we can use in our programs. We can
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create strings by simply writing some text in quotes.
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```python
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>>> 'hello'
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'hello'
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>>> 'this is a test'
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'this is a test'
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>>>
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```
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Strings can also be written with "double quotes" instead of 'single
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quotes'. This is useful when we need to put quotes inside the string.
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```python
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>>> "hello there"
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'hello there'
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>>> "it's sunny"
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"it's sunny"
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>>>
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```
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It's also possible to add single quotes and double quotes into the same
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string, but most of the time we don't need to do that so I'm not going
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to talk about it now.
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It doesn't matter which quotes you use when the string doesn't need to
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contain any quotes. If you think that one of the quote types looks nicer
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than the other or you find it faster to type, go ahead and use that.
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Strings can be joined together easily with `+` or repeated with `*`:
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```python
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>>> "hello" + "world"
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'helloworld'
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>>> "hello" * 3
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'hellohellohello'
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>>>
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```
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Note that a `#` inside a string doesn't create a comment.
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```python
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>>> "strings can contain # characters"
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'strings can contain # characters'
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>>>
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```
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## Using Python as a calculator
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You can also leave out spaces to show what's calculated first. Python
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ignores it, but our code will be easier to read for people.
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```python
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>>> 1 + 2*3 # now it looks like 2*3 is calculated first
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7
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>>>
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```
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Python also supports many other kinds of calculations, but most of the
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time you don't need them. Actually you don't need even these
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calculations most of the time, but these calculations are probably
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- We can enter any Python commands to the interactive `>>>` prompt, and
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it will echo back the result.
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- `+`, `-`, `*` and `/` work in Python just like in math.
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- Pieces of text starting with a `#` are comments.
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- Pieces of text starting with a `#` are comments and pieces of text in
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quotes are strings.
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- You can use single quotes and double quotes however you want.
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***
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‎basics/lists-and-tuples.md

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![Different lists.](../images/differentlist.png)
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If you're using Python 3.2 or older you need to do `a[:]` instead
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of `a.copy()`. `a[:]` is a slice of the whole list, just like
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`a[0:]`.
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## Tuples
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Tuples are a lot like lists, but they're immutable so they

‎basics/loops.md

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>>>
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If you're using Python 3.2 or older you need to use `stuff[:]` instead
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of `stuff.copy()` and `stuff[:] = []` instead of `stuff.clear()`.
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`stuff[:]` is a slice of the whole list, just like `stuff[0:]`.
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## Summary
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- A loop means repeating something multiple times.

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