mccabe

McCabe checker, plugin for flake8

mccabe Permissive license Expat license Active ★ 681 v0.7.0 released 2022-01-24

Install

mccabe on PyPI

pip

pip install mccabe

uv

uv add mccabe

poetry

poetry add mccabe

Package facts

License	Expat license (permissive)
Python support	supports the current Python release (>=3.6)
Install friction	low — pure-Python wheel
Runtime dependencies	none
Maintenance	actively maintained — 1,662 days since the last release
Last repo commit	2026-06-28
First released	2013-02-22
Popularity	one of the top 1,000 most-downloaded packages on PyPI (30-day window, as of 2026-08-13)
Known vulnerabilities	none known (OSV.dev, checked 2026-08-13)

Evidence: mccabe-0.7.0-py2.py3-none-any.whl

Keywords: flake8, mccabe

Development Status :: 5 - Production/StableEnvironment :: ConsoleIntended Audience :: DevelopersLicense :: OSI Approved :: MIT LicenseOperating System :: OS IndependentProgramming Language :: PythonProgramming Language :: Python :: 3.10Programming Language :: Python :: 3.6Programming Language :: Python :: 3.7Programming Language :: Python :: 3.8Programming Language :: Python :: 3.9Topic :: Software Development :: Libraries :: Python ModulesTopic :: Software Development :: Quality Assurance

About mccabe

from the package's own PyPI description — quoted content, verbatim

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, or 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+ 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 than the provided value::

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

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AI-generated interpretation of the package facts above; every digit, version, license, or vulnerability id it cites is grounded in the facts already shown on this page

Measures cyclomatic complexity of Python functions to identify overly complex code; works as a standalone checker or integrates with flake8 to flag functions exceeding a complexity threshold.

Installs cleanly with no runtime dependencies and maintains active development; last release was 2022-01-24 with Python 3.6+ support confirmed.

Licensed under the Expat license (MIT equivalent), a permissive license allowing commercial and private use with minimal restrictions.

Usage

pip install mccabe
python -m mccabe --min 5 yourfile.py

Or integrate with flake8:
flake8 --max-complexity 10 yourproject/

Requires Python 3.6 or later; flake8 integration requires flake8 2.0+ to be installed separately.

Verdict: A mature, actively maintained tool for detecting overly complex functions in Python code. Zero known vulnerabilities, permissive licensing, and zero runtime dependencies make it a low-friction addition to code-quality workflows. Best used as a flake8 plugin or standalone checker to enforce complexity thresholds across a codebase.

Needs verification

Whether the flake8 plugin is automatically discovered or requires explicit configuration beyond --max-complexity
Current adoption rate or download volume relative to other flake8 plugins

cyclomatic complexity checkercode complexity analysis pythonflake8 complexity pluginmccabe complexityfunction complexity measurementdetect complex functionscode quality metrics python