Python Programming Language

The Python programming language is an open source, widely-used tool for creating software applications.

What is Python used for?

Python is often used to build and deploy web applications and web APIs. Python can also analyze and visualize data and test software, even if the software being tested was not written in Python.

Language concepts

Python has several useful programming language concepts that are less frequently found in other languages. These concepts include:

Generators

Generators are a Python core language construct that allow a function's return value to behave as an iterator. A generator can allow more efficient memory usage by allocating and deallocating memory during the context of a large number of iterations. Generators are defined in PEP255 and included in the language as of Python 2.2 in 2001.

Comprehensions

Comprehensions are a Python language construct for concisely creating data in lists, dictionaries and sets. List comprehensions are included in Python 2 while dictionary and set comprehensions were introduced to the language in Python 3.

Why are comprehensions important?

Comprehensions are a more clear syntax for populating conditional data in the core Python data structures. Creating data without comprehensions often involves nested loops with conditionals that can be difficult for code readers to properly evaluate.

Example comprehensions code

List comprehension:

>>> double_digit_evens = [e*2 for e in range(5, 50)]
>>> double_digit_evens
[10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98]

Set comprehension:

>>> double_digit_odds = {e*2+1 for e in range(5, 50)}
{11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99}

Dictionary comprehension:

>>> {e: e*10 for e in range(1, 11)}
{1: 10, 2: 20, 3: 30, 4: 40, 5: 50, 6: 60, 7: 70, 8: 80, 9: 90, 10: 100}

General Python language resources

Python ecosystem resources

There's an entire page on best Python resources with links but the following resources are a better fit for when you're past the very beginner topics.

Comprehension resources

  • Comprehending Python’s Comprehensions is an awesome post by Dan Bader with a slew of examples that explain how list, dictionary and set comprehensions should be used.

  • Python List Comprehensions: Explained Visually explains how the common idiom for iteration became syntactic sugar in the language itself and how you can use it in your own programs.

  • The Python 3 Patterns and Idioms site has an overview of comprehensions including code examples and diagrams to explain how they work.

  • Comprehensions in Python the Jedi way shows off comprehensions with a Star Wars theme to walk through the nuts and bolts. All examples use Python 3.5.

  • Idiomatic Python: Comprehensions explains how Python's comprehensions were inspired by Haskell's list comprehensions. It also provides clear examples that show how comprehensions are shorthand for common iteration code, such as copying one list into another while performing some operation on the contained elements.

  • List comprehensions in Python covers what the code for list comprehensions looks like and gives some example code to show how they work.

  • An Introduction to Python Lists is a solid overview of Python lists in general and tangentially covers list comprehensions.

Python generator resources

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Matt Makai 2012-2019