Cool New Features in Python 3.11 (Summary)

Hello Christopher,

can you talk more about the “Self” keyword or put a better example of it? The official documentation just mention this but there’s no advanced examples. Is it just a syntactic sugar? The same effect we can get using the __future__ built-in package:

from __future__ import annotations

...

class MyClass(SomeBaseClass):
    some_property = property(...)

    def some_method(self) -> MyClass:
        ...
        return self

    @staticmethod
    def some_method_2() -> MyClass:
        ...
        return MyClass(...)

...

m = MyClass()
m_2 = m.some_method()
m_2.[cursor here]       # Type hint will directly show the fields, classes and methods for the MyClass

This works for every type of method, no matter it is an instance method (built-in or custom), @classmethod or @staticmethod.

Hi Marcin,

there are a bit more detail in the examples on realpython.com/python311-new-features/#improved-type-variables and realpython.com/python311-tomllib/#self-type.

As you note, you can use future annotations to add similiar hints without Self. This works well, as long as your class is not subclassed. Consider this continuation of your example:

class MySubclass(MyClass): ...

The return-type of MySubclass.some_method() is MyClass according to the annotation. However, the method is returning self which is a MySubclass object instead. Self will correctly handle this kinds of cases.

Thank you Geir Arne,

I missed the links which you provided but now it’s clear and I see the purpose. However, when I do inherited classes, I create overloaded methods which return proper types and I didn’t even realized that the problem may occur in other situations.