Note: Black, the uncompromising Python code formatter, or add-trailing-comma can do all this comma insertion automatically. We recommend you use one of those tools instead.

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

pip install flake8-commas

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

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

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.