How can I set the same type as class in method's parameter following PEP484? [duplicate]

Question

My question is related with the new Python's type hints. I'm trying to add a type hint in an object's method who has a parameter of the same type of the object, but PyCharm are marking me as error (unresolved reference 'Foo'). The problem is as follows:

class Foo:

    def foo_method(self, other_foo: Foo):
        return "Hello World!"

So the question is how to define the type of other_foo parameter properly. Maybe __class__ is correct?

Answer 1

Inside of the class, the class is not defined yet, causing a NameError (and PyCharm to complain).

To get around this, use forward declarations:

class Foo:
    def foo_method(self, other_foo: "Foo"):
        return "Hello World!"

Basically, if a type annotations is a string, it is evaled after the whole module is loaded, so it can evaluate to the Foo class.