BUG: fix importing numpy in Python's optimized mode - #27868

sure thing. What for would be appropriate ? Do we want to run the whole test suite or just try python -OO -c 'import numpy' ? and where should this new job live ?

The whole test suite, and no new job needed I think - just adding PYTHONOPTIMIZE=2 to the existing full job at https://github.com/numpy/numpy/blob/main/.github/workflows/linux.yml#L153 should cover our bases.

Interesting, this found one failing test under PYTHONOPTIMIZE=2 . Let me try to fix this too.

Only the test itself didn't support optimized mode because it relied on having IO operations evaled through assert statements. Separating evaluation from assertion should do the trick (it works locally, at least).

Does this mean that all the assert in the tests are actually removed? I.e., that full now only tests that the tests run, but not actually that the output is correct? That may not be horrible, but perhaps not quite intended either... Especially as surely there are other tests whether something is calculated inside the assert, and thus coverage may be incomplete too.

I wonder if we can pick a shorter run and just do tests twice, as in

pytest ...
PYTHONOPTIMIZE=2 pytest ...

(Checking this locally on another project, I get a failure because astropy can also not be loaded with -O...)

Alternatively, perhaps we do need a special branch that just imports everything?

Does this mean that all the assert in the tests are actually removed?

yes. That is a direct expectation from running python with PYTHONOPTIMIZE >0

Wasn't that fixed? IIRC that was a main reason for us avoiding plain assert in the past (in favor of our own np.testing.assert_), and pytest got robust against that at some point I believe.

Oh yes, sorry, I see from doing more experiments with it locally that actually, only assert statements that are not part of tests are expected to be skipped. In fact, pytest warns about it

PytestConfigWarning: assertions not in test modules or plugins will be ignored because assert statements are not executed by the underlying Python interpreter (are you using python -O?)

though, I don't understand why that one test needed tweaking...

For reference, pytest indeed rewrites the assert upon import of the test module - https://docs.pytest.org/en/stable/announce/release-2.1.0.html and https://docs.pytest.org/en/stable/how-to/assert.html#assert-details. I'm still not sure why the test needed to be rewritten, though!

My guess is that this is due to:

numpy/_core/tests/test_deprecations.py:        from numpy.lib.tests.test_io import TextIO

i.e. the module is already imported before pytest does its magic. I think it would be nice if pytest would warn (or even error) but dunno if that is doable.

Maybe open an issue there?

So an alternative fix would be moving the TextIO use (or seeing if the deprecation test is even worth it).
EDIT: In fact, it is probably fine to always warn if a test file imports another test file...

But, since that seems the reason, this work-around is also not a big deal.

EDIT: To be clear, the full file has no asserts in this test run. But, it is also only this test file that seems to be imported anywhere.

Thanks @neutrinoceros, @mhvk and @seberg!