You can get compile time validation for this type of construct using typing.Union. But once you have type validation i don't really see the use case anymore. C

You can get compile time validation for this type of construct using typing.Union. But once you have type validation i don't really see the use case anymore. Common example of how silly this is is functions that have a special case for handling lists of length 1 by allowing the object to be passed in without being part of a list, eg Union[List[Foo], Foo]. Now you need extra code to handle that special case in your function and the type annotation becomes more verbose. Much easier to just enforce List[Foo] as the only way to call your function and let the caller call you function as do_stuff([x]) if they only have a single item x. The IDE will complain instantly if you try to call it as do_stuff(x) so there is no risk to accidentally call it like that.