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Public Python API

|Flake8| 3.0.0 presently does not have a public, stable Python API.

When it does it will be located in :mod:`flake8.api` and that will be documented here.

Legacy API

When |Flake8| broke its hard dependency on the tricky internals of pycodestyle, it lost the easy backwards compatibility as well. To help existing users of that API we have :mod:`flake8.api.legacy`. This module includes a couple classes (which are documented below) and a function.

The main usage that the developers of Flake8 observed was using the :func:`~flake8.api.legacy.get_style_guide` function and then calling :meth:`~flake8.api.legacy.StyleGuide.check_files`. To a lesser extent, people also seemed to use the :meth:`~flake8.api.legacy.Report.get_statistics` method on what check_files returns. We then sought to preserve that API in this module.

Let's look at an example piece of code together:

from flake8.api import legacy as flake8


style_guide = flake8.get_style_guide(ignore=['E24', 'W503'])
report = style_guide.check_files([...])
assert report.get_statistics('E') == [], 'Flake8 found violations'

This represents the basic universal usage of all existing Flake8 2.x integrations. Each example we found was obviously slightly different, but this is kind of the gist, so let's walk through this.

Everything that is backwards compatible for our API is in the :mod:`flake8.api.legacy` submodule. This is to indicate, clearly, that the old API is being used.

We create a |StyleGuide| by calling |style_guide|. We can pass options to |style_guide| that correspond to the command-line options one might use. For example, we can pass ignore, select, exclude, format, etc. Our legacy API, does not enforce legacy behaviour, so we can combine ignore and select like we might on the command-line, e.g.,

style_guide = flake8.get_style_guide(
    ignore=['E24', 'W5'],
    select=['E', 'W', 'F'],
    format='pylint',
)

Once we have our |StyleGuide| we can use the same methods that we used before, namely

.. automethod:: flake8.api.legacy.StyleGuide.check_files

.. automethod:: flake8.api.legacy.StyleGuide.excluded

.. automethod:: flake8.api.legacy.StyleGuide.init_report

.. automethod:: flake8.api.legacy.StyleGuide.input_file

Warning

These are not perfectly backwards compatible. Not all arguments are respsected, and some of the types necessary for something to work have changed.

Most people, we observed, were using :meth:`~flake8.api.legacy.StyleGuide.check_files`. You can use this to specify a list of filenames or directories to check. In |Flake8| 3.0, however, we return a different object that has similar methods. We return a |Report| which has the method

.. automethod:: flake8.api.legacy.Report.get_statistics

Most usage of this method that we noted was as documented above. Keep in mind, however, that it provides a list of strings and not anything more maleable.

Autogenerated Legacy Documentation

.. automodule:: flake8.api.legacy
    :members:

.. autoclass:: flake8.api.legacy.StyleGuide
    :members: options, paths

.. autoclass:: flake8.api.legacy.Report
    :members: total_errors