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A flake8 extension that checks cyclomatic complexity and calculates max complexity limit in runtime

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An extension for flake8 to report on too complex functions with bad variables names.

Sometimes you want to use too generic variable name inside some function. It this case you want to be sure that the function is more simple that others, so a reader doesn't have to remember meaning of a variable together with other logic for a long time.

This plugin calculates max allowed cyclomatic complexity for each function separately. Default is 7, and it is decreased by 2 for each variable from blacklist inside the function. If actual complexity overcomes max calculated complexity, the plugin reports an error.

Currently, the following errors are reported:

Code Description
CAC001 func is too complex (complexity > max allowed complexity)
CAC002 func is too complex (complexity). Bad variable names penalty is too high (penalty)


pip install flake8-adjustable-complexity


The plugin has the following configuration options:

  • --max-mccabe-complexity (or --max-adjustable-complexity) - Max allowed cyclomatic complexity.
  • --per-path-max-adjustable-complexity - Per-path complexity settings. The value of the option must be a comma-separated list of <path>:<complexity> pairs.
  • --var-names-extra-blacklist - Comma-separated list of bad variable names to blacklist. Each variable will affect the max allowed complexity.
  • --var-names-whitelist - Comma-separated list of bad variable names to whitelist.

All options also can be specified via [flake8] section of setup.cfg.


Sample file:


def foo():
    for vars in range(5):
        for info in range(5):
            for obj in range(5):


$ flake8 CAC001 foo is too complex (4 > 1)


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

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

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