Fixit is a Python Lint Framework based on LibCST. It comes with useful default lint rules for coding convention, performance and security issues. It makes custom lint rule easy to build, test and configure. It empowers lint rule to provide autofix to fix the issues for developers. It also provide tools to run autofix across codebase to fix existing issues and automatically insert lint-fixme comments to silent existing violation. Fixit integrates with Flake8 and it adds the above mentioned enhancements to it.





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.. intro-start

:title:A lint framework that writes better Python code for you.

Fixit is a lint framework that complements Flake8 <>. It’s based on LibCST <> which makes it possible to provide auto-fixes. Lint rules are made easy to build through pattern matching, a test toolkit, and utility helpers (e.g. scope analysis) for non-trivial boilerplate. It is optimized for efficiency, easy to customize and comes with many builtin lint rules.

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Getting Started

To install Fixit::

pip install fixit

Fixit provides CLI commands. To run built-in Fixit rules on existing code to get code quality suggestions::

python -m fixit.cli.run_rules

To apply autofix on existing code::

python -m fixit.cli.apply_fix

You can learn more about how to configure Fixit <>, build a lint rule <>, test a lint rule <> from our tutorials. Try it out with our notebook examples <>.

Further Reading

  • Static Analysis at Scale: An Instagram Story. <>_


Start by setting up and activating a virtualenv:

.. code-block:: shell

git clone fixit
cd fixit
python3 -m venv ../fixit-env/  # just an example, put this wherever you want
source ../fixit-env/bin/activate
pip install --upgrade pip  # optional, if you have an old system version of pip
pip install -r requirements.txt -r requirements-dev.txt
# If you're done with the virtualenv, you can leave it by running:

We use isort <> and black <> to format code. To format changes to be conformant, run the following in the root:

.. code-block:: shell

tox -e autofix

To run all tests, you'll need to install tox <>_ and do the following in the root: (use py37, py38 to choose from Python version 3.7 or 3.8)::

tox -e py38

You can also run individual unit tests by specifying a module like this::

tox -e py38 -- fixit.common.tests.test_report

To run all test cases of a specific rule (e.g. NoInheritFromObjectRule)::

tox -e py38 -- fixit.tests.NoInheritFromObjectRule

See the unittest documentation <>_ for more examples of how to run tests.

We use Pyre <>_ for type-checking. To verify types for the library, do the following in the root::

pyre --preserve-pythonpath check

To generate documentation, do the following in the root:

.. code-block:: shell

tox -e docs


Fixit is MIT licensed <LICENSE>_, as found in the LICENSE file.

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Privacy Policy and Terms of Use

  • Privacy Policy <>_
  • Terms of Use <>_

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