Flake8 Extension to enforce better comma placement.

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Note: Black <https://pypi.org/project/black/>, the uncompromising Python code formatter, or add-trailing-comma <https://github.com/asottile/add-trailing-comma> can do all this comma insertion automatically. We recommend you use one of those tools instead.

Usage

If you are using flake8 it's as easy as:

.. code:: shell

pip install flake8-commas

Now you can avoid those annoying merge conflicts on dictionary and list diffs.

Errors

Different versions of python require commas in different places. Ignore the errors for languages you don't use in your flake8 config:

+------+-----------------------------------------+ | Code | message | +======+=========================================+ | C812 | missing trailing comma | +------+-----------------------------------------+ | C813 | missing trailing comma in Python 3 | +------+-----------------------------------------+ | C814 | missing trailing comma in Python 2 | +------+-----------------------------------------+ | C815 | missing trailing comma in Python 3.5+ | +------+-----------------------------------------+ | C816 | missing trailing comma in Python 3.6+ | +------+-----------------------------------------+ | C818 | trailing comma on bare tuple prohibited | +------+-----------------------------------------+ | C819 | trailing comma prohibited | +------+-----------------------------------------+

Examples

.. code:: Python

lookup_table = {
    'key1': 'value',
    'key2': 'something'  # <-- missing a trailing comma
}

json_data = json.dumps({
    "key": "value",
}),                      # <-- incorrect trailing comma. json_data is now a tuple. Likely by accident.