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flake8 is a python tool that glues together pycodestyle, pyflakes, mccabe, and third-party plugins to check the style and quality of some python code.
https://flake8.pycqa.org
complexity-analysisflake8linterlinter-flake8pep8pythonpython3static-analysisstatic-code-analysisstyle-guidestyleguidestylelint
d98e1729b3
If someone is using flake8 and piping it to a command like `head`, the command they are piping flake8's output too may close the pipe earlier than flake8 expects. To avoid extraneous exception output being printed, we now catch IOErrors and check their errnos to ensure they're something we know we can ignore. This also provides flexibility to add further errnos for ignoring on a case-by-case basis. Closes #69 |
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======
Flake8
======
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.
QuickStart
==========
::
pip install flake8
To run flake8 just invoke it against any directory or Python module::
$ flake8 coolproject
coolproject/mod.py:97:1: F401 'shutil' imported but unused
coolproject/mod.py:625:17: E225 missing whitespace around operato
coolproject/mod.py:729:1: F811 redefinition of function 'readlines' from line 723
coolproject/mod.py:1028:1: 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/mod.py:97:1: F401 'shutil' imported but unused
coolproject/mod.py:625:17: E225 missing whitespace around operator
coolproject/mod.py:729:1: F811 redefinition of unused 'readlines' from line 723
coolproject/mod.py:939:1: C901 'Checker.check_all' is too complex (12)
coolproject/mod.py:1028:1: F841 local variable 'errors' is assigned to but never used
coolproject/mod.py:1204:1: 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 https://en.wikipedia.org/wiki/Cyclomatic_complexity.
Questions or Feedback
=====================
If you have questions you'd like to ask the developers, or feedback you'd like
to provide, feel free to use the mailing list: code-quality@python.org We
would love to hear from you. Additionally, if you have a feature you'd like to
suggest, the mailing list would be the best place for it.
.. _links:
Links
=====
* `flake8 documentation <http://flake8.readthedocs.org/en/latest/>`_
* `pep8 documentation <http://pep8.readthedocs.org/en/latest/>`_