learn-python

# Playground and Cheatsheet for Learning Python

> 🇺🇦 UKRAINE [IS BEING ATTACKED](https://war.ukraine.ua/) BY RUSSIAN ARMY. CIVILIANS ARE GETTING KILLED. RESIDENTIAL AREAS ARE GETTING BOMBED.
> - Help Ukraine via:
>   - [Serhiy Prytula Charity Foundation](https://prytulafoundation.org/en/)
>   - [Come Back Alive Charity Foundation](https://savelife.in.ua/en/donate-en/)
>   - [National Bank of Ukraine](https://bank.gov.ua/en/news/all/natsionalniy-bank-vidkriv-spetsrahunok-dlya-zboru-koshtiv-na-potrebi-armiyi)
> - More info on [war.ukraine.ua](https://war.ukraine.ua/) and [MFA of Ukraine](https://twitter.com/MFA_Ukraine)

<hr/>

[![Build Status](https://travis-ci.org/trekhleb/learn-python.svg?branch=master)](https://travis-ci.org/trekhleb/learn-python)

> This is a collection of Python scripts that are split by [topics](#table-of-contents) and contain 
code examples with explanations, different use cases and links to further readings.

> _Read this in:_ [_Português_](README.pt-BR.md), [_Español_](README.es-ES.md), [_Traditional Chinese_](README.zh-TW.md), [_Українська_](README.uk-UA.md).

It is a **playground** because you may change or add the code to see how it works 
and [test it out](#testing-the-code) using assertions. It also allows you 
to [lint the code](#linting-the-code) you've wrote and check if it fits to Python code style guide.
Altogether it might make your learning process to be more interactive and it might help you to keep 
code quality pretty high from very beginning.

It is a **cheatsheet** because you may get back to these code examples once you want to recap the 
syntax of [standard Python statements and constructions](#table-of-contents). Also because the 
code is full of assertions you'll be able to see expected functions/statements output right away
without launching them.

> _You might also be interested in 🤖 [Interactive Machine Learning Experiments](https://github.com/trekhleb/machine-learning-experiments)_

## How to Use This Repository

Each Python script in this repository has the following structure:

```python
"""Lists  <--- Name of the topic here

# @see: https://www.learnpython.org/en/Lists  <-- Link to further readings goes here

Here might go more detailed explanation of the current topic (i.e. general info about Lists).
"""


def test_list_type():
    """Explanation of sub-topic goes here.
    
    Each file contains test functions that illustrate sub-topics (i.e. lists type, lists methods).
    """
    
    # Here is an example of how to build a list.  <-- Comments here explain the action
    squares = [1, 4, 9, 16, 25]
    
    # Lists can be indexed and sliced. 
    # Indexing returns the item.
    assert squares[0] == 1  # <-- Assertions here illustrate the result.
    # Slicing returns a new list.
    assert squares[-3:] == [9, 16, 25]  # <-- Assertions here illustrate the result.
```

So normally you might want to do the following:

- [Find the topic](#table-of-contents) you want to learn or recap.
- Read