Two variables of the same and different types

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examples/python-types-at-pyweb-2025-01/generics_two_types.py

def no_problem[T](x: T, y: T) -> None:
    print(type(x).__name__, type(y).__name__)

no_problem(2, 2)
no_problem("hi", "hi")
no_problem("hi", 2)

# -----------------------------
from typing import TypeVar

T = TypeVar('T', int, str)

def the_same(x: T, y: T) -> None:
    print(type(x).__name__, type(y).__name__)

the_same(2, 2)
the_same("hi", "hi")
the_same("hi", 2)


# -----------------------------
Q = TypeVar('Q', int, str)

def different(x: T, y: Q) -> None:
    print(type(x).__name__, type(y).__name__)

different(2, 2)
different("hi", "hi")
different("hi", 2)

$ mypy generics_two_types.py
generics_two_types.py:10:1: error: Value of type variable "T" of "the_same" cannot be "object"  [type-var]
Found 1 error in 1 file (checked 1 source file)