[Python] Why is there no attribute (__orig_class__) on instantiation time? [duplicate]

In Python 3.10, there is no __orig_class__ attribute when an object is creating on intialization. Why isn't this attribute present during object creation? I'm just curious to understand why.

sample:

from typing import Generic, TypeVar

T = TypeVar('T')

class TryToGetTypeParameter(Generic[T]):
def __init__(self):
try:
print("On instancing:")
self._show_type_parameter()
except Exception as e:
print(e)
print("\n")

def _show_type_parameter(self):
print(self.__orig_class__.__args__[0])
print("\n")

def show_type_parameter(self):
print("After instancing:")
self._show_type_parameter()


print("\n")
instanced = TryToGetTypeParameter[int]()
instanced.show_type_parameter()


result:


On instancing:
'TryToGetTypeParameter' object has no attribute '__orig_class__'


After instancing:
<class 'int'>



It was answered on https://stackoverflow.com/a/60984681/12557033

The timing of the orig_class assignment varies by Python version, but currently, it's set after normal object construction has already finished. You will not be able to inspect orig_class during init or new.
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