Python - typing 模块 —— NewType

# NewType
from typing import NewType

UserId = NewType('UserId', int)


def name_by_id(user_id: UserId) -> str:
    print(user_id)


UserId('user')  # Fails type check
num = UserId(5)  # type: int

name_by_id(42)  # Fails type check
name_by_id(UserId(42))  # OK

print(type(UserId(5)))


# 输出结果
42
42
<class 'int'>

# 'output' is of type 'int', not 'UserId'
output = UserId(23413) + UserId(54341)
print(output)
print(type(output))


# 输出结果
77754
<class 'int'>