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the modular source code checker: pep8, pyflakes and co

Project description

Flake8 is a wrapper around these tools:

  • PyFlakes

  • pep8

  • Ned Batchelder’s McCabe script

Flake8 runs all the tools by launching the single flake8 script. It displays the warnings in a per-file, merged output.

It also adds a few features:

  • files that contain this line are skipped:

    # flake8: noqa
  • lines that contain a # noqa comment at the end will not issue warnings.

  • a Git and a Mercurial hook.

  • a McCabe complexity checker.

  • extendable through flake8.extension entry points.


pip install flake8

To run flake8 just invoke it against any directory or Python module:

$ flake8 coolproject
coolproject/ F401 'shutil' imported but unused
coolproject/ E225 missing whitespace around operato
coolproject/ F811 redefinition of function 'readlines' from line 723
coolproject/ F841 local variable 'errors' is assigned to but never used

The outputs of PyFlakes and pep8 (and the optional plugins) are merged and returned.

flake8 offers an extra option: –max-complexity, which will emit a warning if the McCabe complexity of a function is higher than the value. By default it’s deactivated:

$ flake8 --max-complexity 12 coolproject
coolproject/ F401 'shutil' imported but unused
coolproject/ E225 missing whitespace around operator
coolproject/ F811 redefinition of unused 'readlines' from line 723
coolproject/ C901 'Checker.check_all' is too complex (12)
coolproject/ F841 local variable 'errors' is assigned to but never used
coolproject/ C901 'selftest' is too complex (14)

This feature is quite useful to detect over-complex code. According to McCabe, anything that goes beyond 10 is too complex. See


2.0.0 - 2013-02-23

  • Pyflakes errors are prefixed by an F instead of an E

  • McCabe complexity warnings are prefixed by a C instead of a W

  • Flake8 supports extensions through entry points

  • Due to the above support, we require setuptools

  • We publish the documentation

  • Fixes #13: pep8, pyflakes and mccabe become external dependencies

  • Split into, and for better logic

  • Expose our parser for our users

  • New feature: Install git and hg hooks automagically

  • By relying on pyflakes (0.6.1), we also fixed #45 and #35

1.7.0 - 2012-12-21

  • Fixes part of #35: Exception for no WITHITEM being an attribute of Checker for Python 3.3

  • Support stdin

  • Incorporate @phd’s builtins pull request

  • Fix the git hook

  • Update to the latest version

1.6.2 - 2012-11-25

  • fixed the NameError: global name ‘message’ is not defined (#46)

1.6.1 - 2012-11-24

  • fixed the mercurial hook, a change from a previous patch was not properly applied

  • fixed an assumption about warnings/error messages that caused an exception to be thrown when McCabe is used

1.6 - 2012-11-16

  • changed the signatures of the check_file function in flake8/, skip_warning in flake8/ and the check, checkPath functions in flake8/

  • fix --exclude and --ignore command flags (#14, #19)

  • fix the git hook that wasn’t catching files not already added to the index (#29)

  • pre-emptively includes the addition to pep8 to ignore certain lines. Add # nopep8 to the end of a line to ignore it. (#37)

  • check_file can now be used without any special prior setup (#21)

  • unpacking exceptions will no longer cause an exception (#20)

  • fixed crash on non-existent file (#38)

1.5 - 2012-10-13

  • fixed the stdin

  • make sure mccabe catches the syntax errors as warnings

  • pep8 upgrade

  • added max_line_length default value

  • added Flake8Command and entry points is setuptools is around

  • using the setuptools console wrapper when available

1.4 - 2012-07-12

  • git_hook: Only check staged changes for compliance

  • use pep8 1.2

1.3.1 - 2012-05-19

  • fixed support for Python 2.5

1.3 - 2012-03-12

  • fixed false W402 warning on exception blocks.

1.2 - 2012-02-12

  • added a git hook

  • now Python 3 compatible

  • mccabe and pyflakes have warning codes like pep8 now

1.1 - 2012-02-14

  • fixed the value returned by –version

  • allow the flake8: header to be more generic

  • fixed the “hg hook raises ‘physical lines’” bug

  • allow three argument form of raise

  • now uses setuptools if available, for ‘develop’ command

1.0 - 2011-11-29

  • Deactivates by default the complexity checker

  • Introduces the complexity option in the HG hook and the command line.

0.9 - 2011-11-09

  • update pep8 version to 0.6.1

  • mccabe check: gracefully handle compile failure

0.8 - 2011-02-27

  • fixed hg hook

  • discard unexisting files on hook check

0.7 - 2010-02-18

  • Fix pep8 initialization when run through Hg

  • Make pep8 short options work when run through the command line

  • Skip duplicates when controlling files via Hg

0.6 - 2010-02-15

  • Fix the McCabe metric on some loops

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