Python类型提示Type Hints示例详解

def split_str(s):
    strs = s.split(",")

# 'primes' is a list of integers
primes = []  # type: List[int]

# 'captain' is a string (Note: initial value is a problem)
captain = ...  # type: str


class Starship:
    # 'stats' is a class variable
    stats = {}  # type: Dict[str, int]

from typing import List, ClassVar, Dict

# int 变量，默认值为 0
num: int = 0

# bool 变量，默认值为 True
bool_var: bool = True

# 字典变量，默认为空
dict_var: Dict = {}

# 列表变量，且列表元素为 int
primes: List[int] = []


class Starship:
    # 类变量,字典类型,键-字符串,值-整型
    stats: ClassVar[Dict[str, int]] = {}

    # 实例变量，标注了是一个整型
    num: int

from typing import List

# int 变量，默认值为 0
num: int = 0

# bool 变量，默认值为 True
bool_var: bool = True

# 字典变量，默认为空
dict_var: Dict = {}

# 列表变量，且列表元素为 int
primes: List[int] = []


num = "123"
bool_var = 123
dict_var = []
primes = ["1", "2"]

print(num, bool_var, dict_var, primes)


# 输出结果
123 123 [] ['1', '2']

# 正常的元组打包
a = 1, 2, 3

# 加上类型提示的元组打包
t: Tuple[int, ...] = (1, 2, 3)
print(t)

t = 1, 2, 3
print(t)

# py3.8+ 才有的写法
t: Tuple[int, ...] = 1, 2, 3
print(t)

t = 1, 2, 3
print(t)


# 输出结果
(1, 2, 3)
(1, 2, 3)
(1, 2, 3)
(1, 2, 3)

# 正常元组解包
message = (1, 2, 3)
a, b, c = message
print(a, b, c)  # 输出 1 2 3

# 加上类型提示的元组解包
header: str
kind: int
body: Optional[List[str]]

# 不会 warning 的栗子
header, kind, body = ("str", 123, ["1", "2", "3"])

# 会提示 warning 的栗子
header, kind, body = (123, 123, ["1", "2", "3"])

class BasicStarship:
    captain: str = 'Picard'               # 实例变量，有默认值
    damage: int                           # 实例变量，没有默认值
    stats: ClassVar[Dict[str, int]] = {}  # 类变量，有默认值

# 参数 name 类型提示 str，而函数返回值类型提示也是 str
def greeting(name: str) -> str:
    return 'Hello ' + name

 def greeting(name: str, obj: Dict[str, List[int]]) -> None:
    print(name, obj)