If you really go "back in the day", this sort of tool wouldn't exist at all, and you would be expected to do it manually, because there were no easy ways to mod

If you really go "back in the day", this sort of tool wouldn't exist at all, and you would be expected to do it manually, because there were no easy ways to modify the syntax in a space- and comment-preserving way. ;) That was developed for 2to3. Huh. I did not know this - in lib2to3, the "asserts" fixer handles this sort of conversion, so you have the ability already .. so long as you don't use new Python 3.10+ syntax that lib2to3 doesn't handle. See https://docs.python.org/3.7/library/2to3.html#2to3fixer-asserts https://docs.python.org/3.7/library/2to3.html#2to3fixer-asse... . I wonder if serhiy-storchaka (who committed that What's New entry) knows about lib2to3's "asserts" fixer. And if that might be a relevant addition or change to the documentation. Someone who cares about this might want to point it out.