Python-TypedDict/7_generic.py at main · semav-techdev/Python-TypedDict · GitHub

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# A generic TypedDict can be created by inheriting from Generic with a list of type parameters:
from typing import TypedDict, Generic, TypeVar, ReadOnly

from typing import TypeVar, NewType

# without generic
def identity_without(x: int) -> int:
    return x

# Define Generic type "T"
T = TypeVar("T")


def identity_with(x: T) -> T:
    return x

print(identity_with("Simav")) # T is str type
print(identity_with(2)) # T is int type
# ---------------------------------------------------------------------------------
# Generic in TypedDict

T = TypeVar("T")

class Response(
    TypedDict, Generic[T]
):  # it is just a data shape not a class to inheritance from so we have a error
    status: int
    payload: T  # This can be any type; it is generic see implementation below


# Response[T](TypedDict)  is from python 3.12 and above
def func4(response: Response) -> None:
    print(type(response))


# class call creation
response: Response = {"status": 200, "payload": "<html>blahh</html>"}
func4(response)# <class 'dict'>


# We have an error here why?
#because class GenProto try to inheritance Response but it's not a real class it just type
#annotation
class GenProto(Response[T]):
    def meth(self) -> T:
        pass
#see here if i try to instance from Response
response: Response = {"status": 200, "payload": "<html>blahh</html>"}
print(type(response))#it will be <class 'dict'>
#here we create a dict not an object like a real class

class GenProto2[T]:
    def __init__(self, res: Response[T]) -> None:
        self.res = res

    def meth(self) -> T:
        return self.res["payload"]
instance=GenProto2({"status": 200, "payload": "<html>blahh</html>"})
#see here if we have an instance from a real class
print(type(instance)) # <class '__main__.GenProto2'>

""""
Response looks like a class, but it is only used for static typing.
At runtime, it behaves like a dict,
so it cannot be used as a base class for inheritance with methods.
"""