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Xenon is a monitoring tool based on Radon <https://github.com/rubik/radon/>_. It monitors your code's complexity. Ideally, Xenon is run every time you commit code. Through command line options, you can set various thresholds for the complexity of your code. It will fail (i.e. it will exit with a non-zero exit code) when any of these requirements is not met.

With Pip:

.. code-block:: sh

$ pip install xenon

Or download the source and run the setup file (requires setuptools):

.. code-block:: sh

$ python setup.py install

Xenon is tested with Python versions 2.7 and 3.6 to 3.12 as well as PyPy.

Typically you would use Xenon in two scenarios:

1. As a git commit hook: to make sure that your code never exceeds some complexity values.

2. On a continuous integration server: as a part of your build, to keep under control, as above, your code's complexity. See Xenon's .travis.yml file_ for an example usage.

The command line ++++++++++++++++

Everything boils down to Xenon's command line usage. To control which files are analyzed, you use the options -e, --exclude and -i, --ignore. Both accept a comma-separated list of glob patterns. The value usually needs quoting at the command line, to prevent the shell from expanding the pattern (in case there is only one). Every filename is matched against the exclude patterns. Every directory name is matched against the ignore patterns. If any of the patterns matches, Xenon won't even descend into them.

The actual threshold values are defined through these options:

• -a, --max-average: Threshold for the average complexity (across all the codebase).
• -m, --max-modules: Threshold for modules complexity.
• -b, --max-absolute: Absolute threshold for block complexity.

All of these options are inclusive.

An actual example +++++++++++++++++

.. code-block:: sh

$ xenon --max-absolute B --max-modules A --max-average A

or, more succinctly:

.. code-block:: sh

$ xenon -b B -m A -a A

With these options Xenon will exit with a non-zero exit code if any of the following conditions is met:

• At least one block has a rank higher than B (i.e. C, D, E or F).
• At least one module has a rank higher than A.
• The average complexity (among all of the analyzed blocks) is ranked with B or higher.

Pre-commit hook +++++++++++++++

Xenon can be used in combination with pre-commit <https://pre-commit.com/>_ as follows:

.. code-block:: yaml

# monitor code complexity
- repo: https://github.com/rubik/xenon
  rev: v0.9.0
  hooks:
  - id: xenon
    args: ['--max-absolute=B', '--max-modules=B', '--max-average=A']

Note: due to how options are passed to commands by pre-commit, make sure to pass values either with an equals sign like in the above example, or by splitting them as separate list items, e.g. ['--max-absolute', 'B'].

For more information regarding cyclomatic complexity and static analysis in Python, please refer to Radon's documentation, the project on which Xenon is based on:

• More on cyclomatic complexity: http://radon.readthedocs.org/en/latest/intro.html
• More on Radon's ranking: http://radon.readthedocs.org/en/latest/commandline.html#the-cc-command

.. _.travis.yml file: https://github.com/rubik/xenon/blob/master/.travis.yml