https://www.python.org/dev/peps/pep-0488/

Will probably want to see http://bugs.python.org/issue17232 resolved as part of this as well.

Here is a patch that implements PEP 488 **except** for Windows installer stuff. I don't think the Windows changes need to block this patch going in, but I will need someone on Windows to help fix up PC/, PCbuild/, Tools/msi, Lib/distutils/command/bdist_msi.py, and Lib/distutils/command/bdist_wininst.py (if you just search for [pyo] you will find what needs an update).

Otherwise if someone wants to give the patch a review you can feel free, else I will commit it at PyCon (do be aware that if you run tests under -O and -OO there are several failures that have nothing to do with this patch).

I don't actually see any essential changes. The bdist_wininst and bdist_msi changes are just for usage help, and presumably they'll go from "do not compile .py to .pyo (optimized)" to "do not compile .py to optimized .pyc".

I'd prefer to leave the .pyo file association in the installer, since it will affect previous installations.

The only change I see in PC/ is PC/getpathp.c, which is just removing a condition on "o" vs "c", and I don't see anything in PCBuild/ that really needs fixing. (Removing the cleanup code is unnecessary and leaving it in may help make sure the buildbots clean up any old .pyo files after we stop creating them.)

A few minor review comments. Nothing substantial, tbh. Looks good.

Thanks for doing this, Brett.  It's so simple a change yet such a great one. :)

LGTM

New changeset a86d630555bd by Brett Cannon in branch 'default':
Issue #23731: Implement PEP 488.
https://hg.python.org/cpython/rev/a86d630555bd

Thanks to Paul and Eric for the review and everyone who provided input!

New changeset bbdbc4399b52 by Zachary Ware in branch 'default':
Issue #23731: Fix tracemalloc test on Windows.
https://hg.python.org/cpython/rev/bbdbc4399b52