typing使用

使用方式

from typing import List

T1 = List[str]


def test(t1: T1, t2: List[str]):
    print(t1[0].title())
    print(t2[0].title())

创建新类型 NewType

from typing import NewType, NoReturn

# 创建int的子类, 名为UserId
UserIdType = NewType('UserId', int)


# 使用
def name_by_id(user_id: UserIdType) -> NoReturn:
    print(user_id)


# 类型检测错误
UserIdType('user')

# 类型检测成功, 返回原类型 "int"
num = UserIdType(5)

# 类型检测错误, 需要传入UserIdType, 而不是int
name_by_id(42)
# 类型检测成功
name_by_id(UserIdType(42))  # OK

类型变量 TypeVar

from typing import TypeVar, Sequence

# 任意类型
T = TypeVar('T')
# 必须是str或bytes
A = TypeVar('A', str, bytes)


# (any, int) -> [any, ...]
def repeat(x: T, n: int) -> Sequence[T]:
    return [x] * n


# (str/bytes, str/bytes) -> str/bytes
def longest(x: A, y: A) -> A:
    return x if len(x) >= len(y) else y

元祖 Tuple

from typing import Tuple


# 任意类型元组
def t1(t: Tuple):
    pass


# 全为字符串的元组
def t2(t: Tuple[str, ...]):
    pass


# 多个类型有 "..." 时为任意类型
def t3(t: Tuple[str, int, ...]):
    pass

列表 List

使用方式如上的Tuple

from typing import List


# 任意类型
def t1(t: List):
    pass


# 全为字符串
def t2(t: List[str, ...]):
    pass


# 多个类型有 "..." 时为任意类型
def t3(t: List[str, int, ...]):
    pass

字典 Dict

from typing import Dict


# key为字符串 value为int
def t1(t: Dict[str, int]):
    pass

集合 Set

from typing import Set


# 任意类型
def t1(t: Set):
    pass


# 字符串
def t2(t: Set[str]):
    pass

序列类型 Sequence

from typing import Union, Sequence


# int
def t1(t: Sequence[int]):
    pass

可调用类型 Callable

from typing import Callable


def test(c: Callable[[int, str], str]):
    res = c(1, "a")
    # 1a <class 'str'>
    print(res, type(res))


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


test(func)

任意类型 Any

from typing import Any


# 任意类型
def t1(a: Any, b: ...):
    pass


t1(1, 2)
t1("a", "b")

无返回值 NoReturn

from typing import NoReturn

def stop() -> NoReturn:
    raise RuntimeError('no way')

联合类型 Union

from typing import Union


# str或int
def t1(t: Union[str, int]):
    pass

可选类型 Optional

from typing import Optional


# t的类型可以是int
def t1(t: Optional[int] = None):
    pass