The Resolving type hints at runtime says: “For code which uses annotations for other purposes, a regular eval(ann, globals, locals) call is enough to resolve the annotation.”. Without add a new operator `__or__` in type `type`, it’s not possible to resolve type hints at runtime.

>>> from __future__ import annotations
>>> def foo() -> int | str: pass
...
>>> eval(foo.__annotations__['return'])
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<string>", line 1, in <module>
TypeError: unsupported operand type(s) for |: 'type' and 'type'

Le ven. 20 sept. 2019 à 15:35, Sebastian Rittau <srittau@rittau.biz> a écrit :

Am 20.09.19 um 14:49 schrieb Chris Angelico:
> Both "int or str" and "str?" have the problem that they don't work
> under existing Python syntax, so they would be far greater changes.
> The definition of the "or" operator is baked into the language, but
> the "|" operator can have its semantics defined by the objects on
> either side.

"or" works with "from __future__ import annotations", which is a fine
limitation in my opinion.

- Sebastian
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