Python 3.10 新特性介绍

1.上下文管理器

with语句支持一次打开多个上下文管理器：

# Python 3.9
with open('test1.txt') as f1:
  with open('test2.txt') as f2:
    pass

# Python 3.10
with (open('test1.txt') as f1,
      open('test2.txt') as f2):
    pass

2.新增Match case语句

新增类似其它语言的switch case语句结构

status = 404
match status:
  case 400:
    res = 'Bad request'
  case 404:
    res = 'Not found'
  case 500 | 501 | 502 | 503 | 504:
    res = 'Server error'
  case ('error', code, _):
    res = f'An error {code} occurred'
  case _:
    res = 'Something's wrong with the internet'

3.新的类型提示联合运算符

新引入了“X|Y”语法的类型提示联合运算符

# Python 3.9
def add(x: Union[int, float], y: Union[int, float]) -> Union[int, float]:
  return x + y 

# Python 3.10
def add(x: int|float, y: int|float) -> int|float:
  return x + y 

这个新的语法也可以用在isinstance()或issubclass()函数中

isinstance(5, int|str|float)