New submission from flying sheep: typing.Union prevents the use of `isinstance` and `issubclass` via a hook.
This is presumably to prevent errors that would arise if someone tried to do issubclass(A, Union[A, B]) or isinstance(A(), Union[A, B]), because Union isn’t specified in the PEP to allow a check like this, and doesn’t implement it. (Instead it throws said error) However, as far as I can see there is no blessed way to check if an object was returned by Union.__getitem__(). A simple way that works is: sig = inspect.signature(f) ann = sig.parameters['arg1'].annotation is_an_union = isinstance(ann, typing._Union) but _Union is a private class, and an implementation detail. is there a blessed way to do this? If not, one should be added. ---------- components: Library (Lib) messages: 285410 nosy: flying sheep priority: normal severity: normal status: open title: Provide a way to check for *real* typing.Union instances versions: Python 3.6 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue29262> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
