On Sun, May 21, 2017 at 7:29 PM, bartc <b...@freeuk.com> wrote: > > They might be /created/ at runtime, but it's a pretty good bet that the name > A in this declaration: > > class A... > > is the name of a class. The question in Python, as always, is whether an A > used as the name of a type in a type, is still this same A. And presumably > such a type hint can precede the declaration of A. > > In fact the declaration of A might be in a different module from its use in > a type hint, which means that, in the CPython byte-code compiler anyway, it > is not visible at compile-time, when type hints could best be put to good > effect.
That isn't a problem - mypy follows imports. It'd be pretty useless if it didn't :) > Furthermore, both A, and the type-hinting code, might be conditional. So > that on Tuesdays, A is a class, the rest of the week it's the name of a > module. Or, more plausible example: on platforms that have a system-provided source of entropy, random.random is an instance of SystemRandom, but on those that don't, it's an instance of DeterministicRandom with an arbitrarily-chosen seed. The two will have slightly different APIs. > Python doesn't make things easy. Python makes things flexible, which has a cost. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
