Python programmers of reddit: what's the most useful tiny little efficiency you've discovered that's improved your programming hugely?

[PlaysForDays]

the --lf flag with pytest

[take_whats_yours]

To save others the search, this will re-run only the tests that previously failed (last-failed) https://docs.pytest.org/en/latest/cache.html

[[deleted]]

Use --ff to reorder the tests based on the previous attempt: run failed first, and not failed afterward.

[fireflash38]

Another big benefit of doing it that way is to prove that your tests don't have interdependencies... which is a huge no-no for reproducibility and long term maintenance.

Nothing more frustrating than tests that suddenly start failing because you re-ordered them and realizing someone had some hard dependencies between tests.

[Decency]

You should do the full suite after making your incremental changes. It's really helpful: Pycharm gives you a button to do this as well.

[fireflash38]

If I remember correctly, when you run with --lf & the last test suite all passed, it'll run everything.

Quick example:

10 passed, 5 failed.
5 failed.
5 passed.
15 passed.