.. _configuration: ==================== Configuring Flake8 ==================== Once you have learned how to :ref:`invoke ` |Flake8|, you will soon want to learn how to configure it so you do not have to specify the same options every time you use it. This section will show you how to make .. prompt:: bash flake8 Remember that you want to specify certain options without writing .. prompt:: bash flake8 --select E123,W456 --enable-extensions H111 Configuration Locations ======================= |Flake8| supports storing its configuration in your project in one of ``setup.cfg``, ``tox.ini``, or ``.flake8``. Values set at the command line have highest priority, then those in the project configuration file, and finally there are the defaults. However, there are additional command line options which can alter this. Project Configuration --------------------- |Flake8| is written with the understanding that people organize projects into sub-directories. Let's take for example |Flake8|'s own project structure .. code:: flake8 ├── docs │   ├── build │   └── source │   ├── _static │   ├── _templates │   ├── dev │   ├── internal │   └── user ├── flake8 │   ├── formatting │   ├── main │   ├── options │   └── plugins └── tests ├── fixtures │   └── config_files ├── integration └── unit In the top-level ``flake8`` directory (which contains ``docs``, ``flake8``, and ``tests``) there's also ``tox.ini`` and ``setup.cfg`` files. In our case, we keep our |Flake8| configuration in ``tox.ini``. Regardless of whether you keep your config in ``.flake8``, ``setup.cfg``, or ``tox.ini`` we expect you to use INI to configure |Flake8| (since each of these files already uses INI as a format). This means that any |Flake8| configuration you wish to set needs to be in the ``flake8`` section, which means it needs to start like so: .. code-block:: ini [flake8] Each command-line option that you want to specify in your config file can be named in either of two ways: #. Using underscores (``_``) instead of hyphens (``-``) #. Simply using hyphens (without the leading hyphens) .. note:: Not every |Flake8| command-line option can be specified in the configuration file. See :ref:`our list of options ` to determine which options will be parsed from the configuration files. Let's actually look at |Flake8|'s own configuration section: .. code-block:: ini [flake8] ignore = D203 exclude = .git,__pycache__,docs/source/conf.py,old,build,dist max-complexity = 10 This is equivalent to: .. prompt:: bash flake8 --ignore D203 \ --exclude .git,__pycache__,docs/source/conf.py,old,build,dist \ --max-complexity 10 In our case, if we wanted to, we could also do .. code-block:: ini [flake8] ignore = D203 exclude = .git, __pycache__, docs/source/conf.py, old, build, dist max-complexity = 10 This allows us to add comments for why we're excluding items, e.g. .. code-block:: ini [flake8] ignore = D203 exclude = # No need to traverse our git directory .git, # There's no value in checking cache directories __pycache__, # The conf file is mostly autogenerated, ignore it docs/source/conf.py, # The old directory contains Flake8 2.0 old, # This contains our built documentation build, # This contains builds of flake8 that we don't want to check dist max-complexity = 10 .. note:: Following the recommended settings for `Python's configparser `_, |Flake8| does not support inline comments for any of the keys. So while this is fine: .. code-block:: ini [flake8] per-file-ignores = # imported but unused __init__.py: F401 this is not: .. code-block:: ini [flake8] per-file-ignores = __init__.py: F401 # imported but unused .. note:: If you're using Python 2, you will notice that we download the :mod:`configparser` backport from PyPI. That backport enables us to support this behaviour on all supported versions of Python. Please do **not** open issues about this dependency to |Flake8|. .. note:: You can also specify ``--max-complexity`` as ``max_complexity = 10``. This is also useful if you have a long list of error codes to ignore. Let's look at a portion of a project's Flake8 configuration in their ``tox.ini``: .. code-block:: ini [flake8] # it's not a bug that we aren't using all of hacking, ignore: # H101: Use TODO(NAME) # H202: assertRaises Exception too broad # H233: Python 3.x incompatible use of print operator # H301: one import per line # H306: imports not in alphabetical order (time, os) # H401: docstring should not start with a space # H403: multi line docstrings should end on a new line # H404: multi line docstring should start without a leading new line # H405: multi line docstring summary not separated with an empty line # H501: Do not use self.__dict__ for string formatting ignore = H101,H202,H233,H301,H306,H401,H403,H404,H405,H501 They use the comments to describe the check but they could also write this as: .. code-block:: ini [flake8] # it's not a bug that we aren't using all of hacking ignore = # H101: Use TODO(NAME) H101, # H202: assertRaises Exception too broad H202, # H233: Python 3.x incompatible use of print operator H233, # H301: one import per line H301, # H306: imports not in alphabetical order (time, os) H306, # H401: docstring should not start with a space H401, # H403: multi line docstrings should end on a new line H403, # H404: multi line docstring should start without a leading new line H404, # H405: multi line docstring summary not separated with an empty line H405, # H501: Do not use self.__dict__ for string formatting H501 Or they could use each comment to describe **why** they've ignored the check. |Flake8| knows how to parse these lists and will appropriately handle these situations. Using Local Plugins ------------------- .. versionadded:: 3.5.0 |Flake8| allows users to write plugins that live locally in a project. These plugins do not need to use setuptools or any of the other overhead associated with plugins distributed on PyPI. To use these plugins, users must specify them in their configuration file (i.e., ``.flake8``, ``setup.cfg``, or ``tox.ini``). This must be configured in a separate INI section named ``flake8:local-plugins``. Users may configure plugins that check source code, i.e., ``extension`` plugins, and plugins that report errors, i.e., ``report`` plugins. An example configuration might look like: .. code-block:: ini [flake8:local-plugins] extension = MC1 = project.flake8.checkers:MyChecker1 MC2 = project.flake8.checkers:MyChecker2 report = MR1 = project.flake8.reporters:MyReporter1 MR2 = project.flake8.reporters:MyReporter2 |Flake8| will also, however, allow for commas to separate the plugins for example: .. code-block:: ini [flake8:local-plugins] extension = MC1 = project.flake8.checkers:MyChecker1, MC2 = project.flake8.checkers:MyChecker2 report = MR1 = project.flake8.reporters:MyReporter1, MR2 = project.flake8.reporters:MyReporter2 These configurations will allow you to select your own custom reporter plugin that you've designed or will utilize your new check classes. If your package is installed in the same virtualenv that |Flake8| will run from, and your local plugins are part of that package, you're all set; |Flake8| will be able to import your local plugins. However, if you are working on a project that isn't set up as an installable package, or |Flake8| doesn't run from the same virtualenv your code runs in, you may need to tell |Flake8| where to import your local plugins from. You can do this via the ``paths`` option in the ``local-plugins`` section of your config: .. code-block:: ini [flake8:local-plugins] extension = MC1 = myflake8plugin:MyChecker1 paths = ./path/to Relative paths will be interpreted relative to the config file. Multiple paths can be listed (comma separated just like ``exclude``) as needed. If your local plugins have any dependencies, it's up to you to ensure they are installed in whatever Python environment |Flake8| runs in. .. note:: These plugins otherwise follow the same guidelines as regular plugins.