Library to calculate Python functions cognitive complexity via code

pip install cognitive-complexity==1.3.0



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Library to calculate Python functions cognitive complexity via code.


pip install cognitive_complexity


>>> import ast

>>> funcdef = ast.parse("""
... def f(a):
...     return a * f(a - 1)  # +1 for recursion
... """).body[0]

>>> from cognitive_complexity.api import get_cognitive_complexity
>>> get_cognitive_complexity(funcdef)

Flake8-Cognitive-Complexity Extension

Perhaps the most common way to use this library (especially if you are already using the Flake8 linter) is to use the flake8-cognitive-complexity extension. If you run Flake8 with this extension installed, Flake8 will let you know if your code is too complex. For more details and documentation, visit the flake8-cognitive-complexity extension repository.

What is cognitive complexity

Here are some readings about cognitive complexity:

Realization details

This is not precise realization of original algorithm proposed by G. Ann Campbell, but it gives rather similar results. The algorithm gives complexity points for breaking control flow, nesting, recursion, stacks logic operation etc.


We would love you to contribute to our project. It's simple:

  • Create an issue with bug you found or proposal you have. Wait for approve from maintainer.
  • Create a pull request. Make sure all checks are green.
  • Fix review comments if any.
  • Be awesome.

Here are useful tips:

  • You can run all checks and tests with make check. Please do it before TravisCI does.
  • We use BestDoctor python styleguide. Sorry, styleguide is available only in Russian for now.
  • We respect Django CoC. Make soft, not bullshit.