On Tue, Jul 9, 2019 at 4:15 PM Andrew Barnert via Python-ideas <
python-ideas@python.org> wrote:
> On Jul 9, 2019, at 13:09, Shay Cohen <sha...@gmail.com> wrote:
> >
> > >>> a: 3
>
> The reason this isn’t a syntax error is that Python allows any valid
> expression as an annotation. And “3” is just as valid an expression as
> “int”.
>
> More generally, annotations don’t actually do anything at runtime, except
> get stored in an annotation dictionary.
>
If you're curious where those annotation "definitions" actually disappear
off to: `__annotations__`
>>> a: 3
>>> __annotations__
{'a': 3}
>>> class X:
... b: 42
...
>>> hasattr(X, 'b')
False
>>> X.__annotations__
{'b': 42}
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