I maintain a library for doing exactly this in C# (https://github.com/mcintyre321/OneOf). I tried to replicate it in Python as I'm writing it at the moment, but couldn't quite manage it. Can you have a multi generic typed Union in python?
T1 = TypeVar("T1")
T2 = TypeVar("T2")
GenericUnion = Union[T1, T2] def foo() -> OneOf[Bar, Baz]:
if blah():
return Bar()
return Baz()
def bar_to_blah(bar:Bar) -> Blah :
...
def baz_to_blah(baz:Baz) -> Blah :
...
one_of_bar_or_baz = foo()
blah = one_of_bar_or_baz.match(bar_to_blah, baz_to_blah)