McCabe complexity checker
=========================

Ned's script to check McCabe complexity.

This module provides a plugin for ``flake8``, the Python code checker.


Installation
------------

You can install, upgrade, uninstall ``mccabe`` with these commands::

  $ pip install mccabe
  $ pip install --upgrade mccabe
  $ pip uninstall mccabe


Standalone script
-----------------

The complexity checker can be used directly::

  $ python -m mccabe --min 5 mccabe.py
  ("185:1: 'PathGraphingAstVisitor.visitIf'", 5)
  ("71:1: 'PathGraph.to_dot'", 5)
  ("245:1: 'McCabeChecker.run'", 5)
  ("283:1: 'main'", 7)
  ("203:1: 'PathGraphingAstVisitor.visitTryExcept'", 5)
  ("257:1: 'get_code_complexity'", 5)


Plugin for Flake8
-----------------

When both ``flake8 2.0`` and ``mccabe`` are installed, the plugin is
available in ``flake8``::

  $ flake8 --version
  2.0 (pep8: 1.4.2, pyflakes: 0.6.1, mccabe: 0.2)

By default the plugin is disabled.  Use the ``--max-complexity`` switch to
enable it.  It will emit a warning if the McCabe complexity of a function is
higher that the value::

    $ flake8 --max-complexity 10 coolproject
    ...
    coolproject/mod.py:1204:1: C901 'CoolFactory.prepare' 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.


Links
-----

* Feedback and ideas: http://mail.python.org/mailman/listinfo/code-quality

* Cyclomatic complexity: http://en.wikipedia.org/wiki/Cyclomatic_complexity.

* Ned Batchelder's script:
  http://nedbatchelder.com/blog/200803/python_code_complexity_microtool.html


Changes
-------

0.6.1 - 2017-01-26
``````````````````

* Fix signature for ``PathGraphingAstVisitor.default`` to match the signature
  for ``ASTVisitor``

0.6.0 - 2017-01-23
``````````````````

* Add support for Python 3.6

* Fix handling for missing statement types

0.5.3 - 2016-12-14
``````````````````

* Report actual column number of violation instead of the start of the line

0.5.2 - 2016-07-31
``````````````````

* When opening files ourselves, make sure we always name the file variable

0.5.1 - 2016-07-28
``````````````````

* Set default maximum complexity to -1 on the class itself

0.5.0 - 2016-05-30
``````````````````

* PyCon 2016 PDX release

* Add support for Flake8 3.0

0.4.0 - 2016-01-27
``````````````````

* Stop testing on Python 3.2

* Add support for async/await keywords on Python 3.5 from PEP 0492

0.3.1 - 2015-06-14
``````````````````

* Include ``test_mccabe.py`` in releases.

* Always coerce the ``max_complexity`` value from Flake8's entry-point to an
  integer.

0.3 - 2014-12-17
````````````````

* Computation was wrong: the mccabe complexity starts at 1, not 2.

* The ``max-complexity`` value is now inclusive.  E.g.: if the
  value is 10 and the reported complexity is 10, then it passes.

* Add tests.


0.2.1 - 2013-04-03
``````````````````

* Do not require ``setuptools`` in setup.py.  It works around an issue
  with ``pip`` and Python 3.


0.2 - 2013-02-22
````````````````

* Rename project to ``mccabe``.

* Provide ``flake8.extension`` setuptools entry point.

* Read ``max-complexity`` from the configuration file.

* Rename argument ``min_complexity`` to ``threshold``.


0.1 - 2013-02-11
````````````````
* First release