pep8
pep8 is a tool to check your Python code against some of the style conventions in PEP 8.
- Plugin architecture: Adding new checks is easy.
- Parseable output: Jump to error location in your editor.
- Small: Just one Python file, requires only stdlib. You can use just the pep8.py file for this purpose.
- Comes with a comprehensive test suite.
This utility does not enforce every single rule of PEP 8. It helps to verify that some coding conventions are applied but it does not intend to be exhaustive. Some rules cannot be expressed with a simple algorithm, and other rules are only guidelines which you could circumvent when you need to.
Always remember this statement from PEP 8:
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.
Among other things, these features are currently not in the scope of the pep8 library:
- naming conventions: this kind of feature is supported through plugins. Install flake8 and the pep8-naming extension to use this feature.
- docstring conventions: they are not in the scope of this library; see the pydocstyle project.
- automatic fixing: see the section PEP8 Fixers in the
related tools <related-tools>page.
You can install, upgrade, uninstall pep8.py with these commands:
$ pip install pep8
$ pip install --upgrade pep8
$ pip uninstall pep8There's also a package for Debian/Ubuntu, but it's not always the latest version:
$ sudo apt-get install pep8$ pep8 --first optparse.py
optparse.py:69:11: E401 multiple imports on one line
optparse.py:77:1: E302 expected 2 blank lines, found 1
optparse.py:88:5: E301 expected 1 blank line, found 0
optparse.py:222:34: W602 deprecated form of raising exception
optparse.py:347:31: E211 whitespace before '('
optparse.py:357:17: E201 whitespace after '{'
optparse.py:472:29: E221 multiple spaces before operator
optparse.py:544:21: W601 .has_key() is deprecated, use 'in'You can also make pep8.py show the source code for each error, and even the relevant text from PEP 8:
$ pep8 --show-source --show-pep8 testsuite/E40.py
testsuite/E40.py:2:10: E401 multiple imports on one line
import os, sys
^
Imports should usually be on separate lines.
Okay: import os\nimport sys
E401: import sys, osOr you can display how often each error was found:
$ pep8 --statistics -qq Python-2.5/Lib
232 E201 whitespace after '['
599 E202 whitespace before ')'
631 E203 whitespace before ','
842 E211 whitespace before '('
2531 E221 multiple spaces before operator
4473 E301 expected 1 blank line, found 0
4006 E302 expected 2 blank lines, found 1
165 E303 too many blank lines (4)
325 E401 multiple imports on one line
3615 E501 line too long (82 characters)
612 W601 .has_key() is deprecated, use 'in'
1188 W602 deprecated form of raising exceptionYou can also make pep8.py show the error text in different formats by using --format having options default/pylint/custom:
$ pep8 testsuite/E40.py --format=default
testsuite/E40.py:2:10: E401 multiple imports on one line
$ pep8 testsuite/E40.py --format=pylint
testsuite/E40.py:2: [E401] multiple imports on one line
$ pep8 testsuite/E40.py --format='%(path)s|%(row)d|%(col)d| %(code)s %(text)s'
testsuite/E40.py|2|10| E401 multiple imports on one lineVariables in the custom format option
| Variable | Significance |
|---|---|
path |
File name |
row |
Row number |
col |
Column number |
code |
Error code |
text |
Error text |
Quick help is available on the command line:
$ pep8 -h
Usage: pep8 [options] input ...
Options:
--version show program's version number and exit
-h, --help show this help message and exit
-v, --verbose print status messages, or debug with -vv
-q, --quiet report only file names, or nothing with -qq
--first show first occurrence of each error
--exclude=patterns exclude files or directories which match these comma
separated patterns (default: .svn,CVS,.bzr,.hg,.git)
--filename=patterns when parsing directories, only check filenames matching
these comma separated patterns (default: *.py)
--select=errors select errors and warnings (e.g. E,W6)
--ignore=errors skip errors and warnings (e.g. E4,W)
--show-source show source code for each error
--show-pep8 show text of PEP 8 for each error (implies --first)
--statistics count errors and warnings
--count print total number of errors and warnings to standard
error and set exit code to 1 if total is not null
--max-line-length=n set maximum allowed line length (default: 79)
--hang-closing hang closing bracket instead of matching indentation of
opening bracket's line
--format=format set the error format [default|pylint|<custom>]
--diff report only lines changed according to the unified diff
received on STDIN
Testing Options:
--benchmark measure processing speed
Configuration:
The project options are read from the [pep8] section of the tox.ini
file or the setup.cfg file located in any parent folder of the path(s)
being processed. Allowed options are: exclude, filename, select,
ignore, max-line-length, hang-closing, count, format, quiet, show-pep8,
show-source, statistics, verbose.
--config=path user config file location (default: ~/.config/pep8)The behaviour may be configured at two levels, the user and project levels.
At the user level, settings are read from the following locations:
- If on Windows:
~\.pep8- Otherwise, if the
XDG_CONFIG_HOMEenvironment variable is defined: XDG_CONFIG_HOME/pep8- Else if
XDG_CONFIG_HOMEis not defined: ~/.config/pep8
Example:
[pep8]
ignore = E226,E302,E41
max-line-length = 160At the project level, a setup.cfg file or a tox.ini file is read if present (.pep8 file is also supported, but it is deprecated). If none of these files have a [pep8] section, no project specific configuration is loaded.
This is the current list of error and warning codes:
+------------+----------------------------------------------------------------------+ | code | sample message | +============+======================================================================+ | E1 | Indentation | +------------+----------------------------------------------------------------------+ | E101 | indentation contains mixed spaces and tabs | +------------+----------------------------------------------------------------------+ | E111 | indentation is not a multiple of four | +------------+----------------------------------------------------------------------+ | E112 | expected an indented block | +------------+----------------------------------------------------------------------+ | E113 | unexpected indentation | +------------+----------------------------------------------------------------------+ | E114 | indentation is not a multiple of four (comment) | +------------+----------------------------------------------------------------------+ | E115 | expected an indented block (comment) | +------------+----------------------------------------------------------------------+ | E116 | unexpected indentation (comment) | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | E121 (*^) | continuation line under-indented for hanging indent | +------------+----------------------------------------------------------------------+ | E122 (^) | continuation line missing indentation or outdented | +------------+----------------------------------------------------------------------+ | E123 () | closing bracket does not match indentation of opening bracket's line | +------------+----------------------------------------------------------------------+ | E124 (^) | closing bracket does not match visual indentation | +------------+----------------------------------------------------------------------+ | E125 (^) | continuation line with same indent as next logical line | +------------+----------------------------------------------------------------------+ | E126 (*^) | continuation line over-indented for hanging indent | +------------+----------------------------------------------------------------------+ | E127 (^) | continuation line over-indented for visual indent | +------------+----------------------------------------------------------------------+ | E128 (^) | continuation line under-indented for visual indent | +------------+----------------------------------------------------------------------+ | E129 (^) | visually indented line with same indent as next logical line | +------------+----------------------------------------------------------------------+ | E131 (^) | continuation line unaligned for hanging indent | +------------+----------------------------------------------------------------------+ | E133 () | closing bracket is missing indentation | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | E2 | Whitespace | +------------+----------------------------------------------------------------------+ | E201 | whitespace after '(' | +------------+----------------------------------------------------------------------+ | E202 | whitespace before ')' | +------------+----------------------------------------------------------------------+ | E203 | whitespace before ':' | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | E211 | whitespace before '(' | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | E221 | multiple spaces before operator | +------------+----------------------------------------------------------------------+ | E222 | multiple spaces after operator | +------------+----------------------------------------------------------------------+ | E223 | tab before operator | +------------+----------------------------------------------------------------------+ | E224 | tab after operator | +------------+----------------------------------------------------------------------+ | E225 | missing whitespace around operator | +------------+----------------------------------------------------------------------+ | E226 () | missing whitespace around arithmetic operator | +------------+----------------------------------------------------------------------+ | E227 | missing whitespace around bitwise or shift operator | +------------+----------------------------------------------------------------------+ | E228 | missing whitespace around modulo operator | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | E231 | missing whitespace after ',', ';', or ':' | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | E241 () | multiple spaces after ',' | +------------+----------------------------------------------------------------------+ | E242 () | tab after ',' | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | E251 | unexpected spaces around keyword / parameter equals | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | E261 | at least two spaces before inline comment | +------------+----------------------------------------------------------------------+ | E262 | inline comment should start with '# ' | +------------+----------------------------------------------------------------------+ | E265 | block comment should start with '# ' | +------------+----------------------------------------------------------------------+ | E266 | too many leading '#' for block comment | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | E271 | multiple spaces after keyword | +------------+----------------------------------------------------------------------+ | E272 | multiple spaces before keyword | +------------+----------------------------------------------------------------------+ | E273 | tab after keyword | +------------+----------------------------------------------------------------------+ | E274 | tab before keyword | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ |E3* | Blank line | +------------+----------------------------------------------------------------------+ | E301 | expected 1 blank line, found 0 | +------------+----------------------------------------------------------------------+ | E302 | expected 2 blank lines, found 0 | +------------+----------------------------------------------------------------------+ | E303 | too many blank lines (3) | +------------+----------------------------------------------------------------------+ | E304 | blank lines found after function decorator | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | E4 | Import | +------------+----------------------------------------------------------------------+ | E401 | multiple imports on one line | +------------+----------------------------------------------------------------------+ | E402 | module level import not at top of file | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | E5 | Line length | +------------+----------------------------------------------------------------------+ | E501 (^) | line too long (82 > 79 characters) | +------------+----------------------------------------------------------------------+ | E502 | the backslash is redundant between brackets | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | E7 | Statement | +------------+----------------------------------------------------------------------+ | E701 | multiple statements on one line (colon) | +------------+----------------------------------------------------------------------+ | E702 | multiple statements on one line (semicolon) | +------------+----------------------------------------------------------------------+ | E703 | statement ends with a semicolon | +------------+----------------------------------------------------------------------+ | E704 () | multiple statements on one line (def) | +------------+----------------------------------------------------------------------+ | E711 (^) | comparison to None should be 'if cond is None:' | +------------+----------------------------------------------------------------------+ | E712 (^) | comparison to True should be 'if cond is True:' or 'if cond:' | +------------+----------------------------------------------------------------------+ | E713 | test for membership should be 'not in' | +------------+----------------------------------------------------------------------+ | E714 | test for object identity should be 'is not' | +------------+----------------------------------------------------------------------+ | E721 (^) | do not compare types, use 'isinstance()' | +------------+----------------------------------------------------------------------+ | E731 | do not assign a lambda expression, use a def | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ |E9* | Runtime | +------------+----------------------------------------------------------------------+ | E901 | SyntaxError or IndentationError | +------------+----------------------------------------------------------------------+ | E902 | IOError | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | W1 | Indentation warning | +------------+----------------------------------------------------------------------+ | W191 | indentation contains tabs | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | W2 | Whitespace warning | +------------+----------------------------------------------------------------------+ | W291 | trailing whitespace | +------------+----------------------------------------------------------------------+ | W292 | no newline at end of file | +------------+----------------------------------------------------------------------+ | W293 | blank line contains whitespace | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | W3 | Blank line warning | +------------+----------------------------------------------------------------------+ | W391 | blank line at end of file | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | W5 | Line break warning | +------------+----------------------------------------------------------------------+ | W503 | line break occurred before a binary operator | +------------+----------------------------------------------------------------------+ +------------+----------------------------------------------------------------------+ | W6 | Deprecation warning | +------------+----------------------------------------------------------------------+ | W601 | .has_key() is deprecated, use 'in' | +------------+----------------------------------------------------------------------+ | W602 | deprecated form of raising exception | +------------+----------------------------------------------------------------------+ | W603 | '<>' is deprecated, use '!=' | +------------+----------------------------------------------------------------------+ | W604 | backticks are deprecated, use 'repr()' | +------------+----------------------------------------------------------------------+
(*) In the default configuration, the checks E121, E123, E126, E133, E226, E241, E242 and E704 are ignored because they are not rules unanimously accepted, and PEP 8 does not enforce them. The check E133 is mutually exclusive with check E123. Use switch --hang- closing to report E133 instead of E123.
(^) These checks can be disabled at the line level using the # noqa special comment. This possibility should be reserved for special cases.
Special cases aren't special enough to break the rules.
Note: most errors can be listed with such one-liner:
$ python pep8.py --first --select E,W testsuite/ --format '%(code)s: %(text)s'The flake8 checker is a wrapper around pep8 and similar tools. It supports plugins.
Other tools which use pep8 are referenced in the Wiki: list of related tools.