Introduction
This document gives coding conventions for the Python code comprising the
standard library in the main Python distribution. Please see the
companion informational PEP describing style guidelines for the C code in
the C implementation of Python[1].
This document was adapted from Guido's original Python Style Guide
essay[2], with some additions from Barry's style guide[5]. Where there's
conflict, Guido's style rules for the purposes of this PEP. This PEP may
still be incomplete (in fact, it may never be finished <wink>).
A Foolish Consistency is the Hobgoblin of Little Minds
One of Guido's key insights is that code is read much more often than it
is written. The guidelines provided here are intended to improve the
readability of code and make it consistent across the wide spectrum of
Python code. As PEP 20 [6] says, "Readability counts".
A style guide is about consistency. Consistency with this style guide is
important. Consistency within a project is more important. Consistency
within one module or function is most important.
But most importantly: know when to be inconsistent -- sometimes the style
guide just doesn't apply. When in doubt, use your best judgment. Look
at other examples and decide what looks best. And don't hesitate to ask!
Two good reasons to break a particular rule:
(1) When applying the rule would make the code less readable, even for
someone who is used to reading code that follows the rules.
(2) To be consistent with surrounding code that also breaks it (maybe for
historic reasons) -- although this is also an opportunity to clean up
someone else's mess (in true XP style).
Code lay-out
Indentation
Use 4 spaces per indentation level.
For really old code that you don't want to mess up, you can continue to
use 8-space tabs.
Continuation lines should align wrapped elements either vertically using
Python's implicit line joining inside parentheses, brackets and braces, or
using a hanging indent. When using a hanging indent the following
considerations should be applied; there should be no arguments on the
first line and further indentation should be used to clearly distinguish
itself as a continuation line.
Yes: # Aligned with opening delimiter
foo = long_function_name(var_one, var_two,
