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Project Notes

flake8-blame

Who busted Python style-guide rules?

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Notes

Personally, I find flake8 the most pragmatic style-guide check for Python.

In Python projects, I’ll often also run pylint as part of CI, but without excessive effort to customise the rules, it is prone to throw lot’s of what we’d call “false positives”. flake8 is much easier to tame.

Now when flake8 is reporting errors it is often useful to know who/what commits/what stories introduced the error. AFAIK, flake8 doesn’t help you do that directly. But here’s a one-liner that will take the flake8 output and git blame the offending lines:

flake8 | awk -F ':' '{print $2 "," $2, $1}' | xargs -n2 git blame -f -L

This is available in the shell script flake8-blame.sh

Example

Say you have a project that is currently reporting a few errors:

$ flake8 .
./api/tests/test_one.py:7:1: E303 too many blank lines (3)
./api/tests/test_one.py:11:58: E251 unexpected spaces around keyword / parameter equals
./api/tests/test_two.py:38:39: E225 missing whitespace around operator

Then the one-liner can help pin-down the commit and commiter:

$ flake8 | awk -F ':' '{print $2 "," $2, $1}' | xargs -n2 git blame -f -L
f6aeee433a snowflake/api/tests/test_one.py (Paul Gallagher 2018-10-03 18:19:08 +0800 7) class TestSomething(ScenarioTestBase):
f9cb75650b snowflake/api/tests/test_one.py (Paul Gallagher 2018-10-03 19:39:01 +0800 11)         self.some_function(max_devices= 2)
f9cb75650b snowflake/api/tests/test_two.py (Paul Gallagher 2018-10-03 19:39:01 +0800 38)         self.some_attribute =None

Note: this may not be exact as the way that errors are reporting may not identify the correct line to blame. For example, E303 too many blank lines in the example above says the error occurred on the first line after the blank lines, so the commit details don’t actually identify the erroneous commit correctly.

Credits and References

About LCK#73 pythonBash
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This page is a web-friendly rendering of my project notes shared in the LittleCodingKata GitHub repository.

LittleCodingKata is my collection of programming exercises, research and code toys broadly spanning things that relate to programming and software development (languages, frameworks and tools).

These range from the trivial to the complex and serious. Many are inspired by existing work and I'll note credits and references where applicable. The focus is quite scattered, as I variously work on things new and important in the moment, or go back to revisit things from the past.

This is primarily a personal collection for my own edification and learning, but anyone who stumbles by is welcome to borrow, steal or reference the work here. And if you spot errors or issues I'd really appreciate some feedback - create an issue, send me an email or even send a pull-request.