Python类型注解必备利器typing模块全面解读

from typing import List

def process_numbers(numbers: List[int]) -> int:
    return sum(numbers)

from typing import Union

def double_or_square(number: Union[int, float]) -> Union[int, float]:
    if isinstance(number, int):
        return number * 2
    else:
        return number ** 2

from typing import Optional

def greet(name: Optional[str]) -> str:
    if name:
        return f"Hello, {name}!"
    else:
        return "Hello, World!"

from typing import TypeVar, List

T = TypeVar('T')

def get_first_element(items: List[T]) -> T:
    return items[0]

first_element = get_first_element([1, 2, 3])  # 推导类型为 int

from typing import Callable, Sequence

def apply_function(
    func: Callable[[int, int], int],
    numbers: Sequence[int]
) -> List[int]:
    return [func(num, num) for num in numbers]

def add(a: int, b: int) -> int:
    return a + b

class MyClass:
    value: int

    def __init__(self, initial_value: int) -> None:
        self.value = initial_value

    def double_value(self) -> int:
        return self.value * 2

from typing import Generator

def generate_numbers(n: int) -> Generator[int, None, None]:
    for i in range(n):
        yield i

from typing import List, Dict, Union

Tree = List[Union[int, Dict[str, 'Tree']]]

UserId = int
Username = str

def get_user_details(user_id: UserId) -> Tuple[UserId, Username]:
    # some code

$ mypy your_program.py