Python

The Python programming language.

Learn

Official tutorial
https://realpython.com
https://matt.sh/python-project-structure-2024
#todo Python Cookbook

Notes

There is no ++ operator, only += 1.
None instead of null.
and instead of &&, or instead of ||.
Division: / is decimal, // is integer.
Numbers are infinite, so they never overflow.
Negative indexes are used to get values starting from the end of a list, so list[-1] is the last value.
For loops: use range() for index only scan, use enumerate() for index and value scan.
List comprehensions return a list: list = [x*x for x in y if z]
Generator expressions return an iterator: iter = (x*x for x in y if z)
List values are loaded into memory immediately, while iterator values are computed lazily.
Rule of thumb: use for loops for modifying lists, use list comprehensions for creating new lists.

Testing

The standard unit testing module is unittest. The file naming convention is test_*.py.

Test template:

import unittest

class TestFoo(unittest.TestCase):
    def test_foo(self) -> None:
        self.assertEqual(1, 2)

if __name__ == "__main__":
    unittest.main()

A popular alternative is pytest.

Virtual environment

A directory that contains an isolated runtime and local pip dependencies. Should be created for each project instead of using the global pip.

Create: python3 -m venv .venv
Activate: source .venv/bin/activate
Deactivate: deactivate

Tooling

Formatter: https://github.com/psf/black
Linter: https://github.com/astral-sh/ruff
Type checker: https://github.com/python/mypy
Language server: https://github.com/microsoft/pyright