Python类型注解举例超详细指南

# 变量注解
name: str = "Alice"
age: int = 30
price: float = 19.99
is_active: bool = True

# 函数参数和返回值注解
def greet(name: str) -> str:
    return f"Hello, {name}"

from typing import List, Dict, Tuple, Set, Optional

# 列表
numbers: List[int] = [1, 2, 3]

# 字典
person: Dict[str, str] = {"name": "Alice", "email": "alice@example.com"}

# 元组 (固定长度和类型)
point: Tuple[float, float] = (3.14, 2.71)

# 集合
unique_numbers: Set[int] = {1, 2, 3}

# 可选类型 (表示可能是None)
middle_name: Optional[str] = None

from typing import Callable

# 基本函数注解
def add(a: int, b: int) -> int:
    return a + b

# 带默认值的参数
def greet(name: str, greeting: str = "Hello") -> str:
    return f"{greeting}, {name}"

# 函数作为参数
def apply_func(func: Callable[[int, int], int], x: int, y: int) -> int:
    return func(x, y)

from typing import Any, Union, NoReturn

# Any - 任意类型
def log(message: Any) -> None:
    print(message)

# Union - 多个可能的类型
def square(number: Union[int, float]) -> Union[int, float]:
    return number ** 2

# NoReturn - 函数不会正常返回
def fail() -> NoReturn:
    raise Exception("Something went wrong")

from typing import List, Tuple

# 简单别名
UserId = int

# 复杂别名
Point = Tuple[float, float]
Vector = List[float]

def normalize(vector: Vector) -> Vector:
    length = sum(x**2 for x in vector) ** 0.5
    return [x/length for x in vector]

from typing import TypeVar, Generic, List

T = TypeVar('T')  # 声明类型变量

class Stack(Generic[T]):
    def __init__(self) -> None:
        self.items: List[T] = []
    
    def push(self, item: T) -> None:
        self.items.append(item)
    
    def pop(self) -> T:
        return self.items.pop()

# 使用
int_stack = Stack[int]()
int_stack.push(1)

from typing import TypeVar, Union

# 无约束的类型变量
T = TypeVar('T')

# 约束的类型变量
Number = TypeVar('Number', int, float, complex)

def double(x: Number) -> Number:
    return x * 2

from typing import NewType, TypedDict

# 新类型
UserId = NewType('UserId', int)

def get_user_name(user_id: UserId) -> str:
    return f"user_{user_id}"

# 类型化字典 (Python 3.8+)
class Person(TypedDict):
    name: str
    age: int
    email: Optional[str]

person: Person = {"name": "Alice", "age": 30}

pip install mypy

mypy your_script.py