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.. _formatting-plugins:
===========================================
Developing a Formatting Plugin for Flake8
===========================================
|Flake8| allowed for custom formatting plugins in version
3.0.0. Let's write a plugin together:
.. code-block:: python
from flake8.formatting import base
class Example(base.BaseFormatter):
"""Flake8's example formatter."""
pass
We notice, as soon as we start, that we inherit from |Flake8|'s
:class:`~flake8.formatting.base.BaseFormatter` class. If we follow the
:ref:`instructions to register a plugin <register-a-plugin>` and try to use
our example formatter, e.g., ``flake8 --format=example`` then
|Flake8| will fail because we did not implement the ``format`` method.
Let's do that next.
.. code-block:: python
class Example(base.BaseFormatter):
"""Flake8's example formatter."""
def format(self, error):
return 'Example formatter: {0!r}'.format(error)
With that we're done. Obviously this isn't a very useful formatter, but it
should highlight the simplicity of creating a formatter with Flake8. If we
wanted to instead create a formatter that aggregated the results and returned
XML, JSON, or subunit we could also do that. |Flake8| interacts with the
formatter in two ways:
#. It creates the formatter and provides it the options parsed from the
configuration files and command-line
#. It uses the instance of the formatter and calls ``handle`` with the error.
By default :meth:`flake8.formatting.base.BaseFormatter.handle` simply calls
the ``format`` method and then ``write``. Any extra handling you wish to do
for formatting purposes should override the ``handle`` method.
API Documentation
=================
.. autoclass:: flake8.formatting.base.BaseFormatter
:members:
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