菜鸟教程《Python 3 教程》笔记（10）：条件控制

10 条件控制

出处： 菜鸟教程 - Python3 条件控制

10.1 match…case

Python 3.10 增加了 match...case 的条件判断。match 后的对象会依次与 case 后的内容进行匹配，如果匹配成功，则执行匹配到的表达式，否则直接跳过，_ 可以匹配一切。

语法：

match subject:
    case <pattern_1>:
        <action_1>
    case <pattern_2>:
        <action_2>
    case <pattern_3>:
        <action_3>
    case _:
        <action_wildcard>

10.1.1 基本模式匹配

x = 10
match x:
    case 10:
        print("x is 10")
    case 20:
        print("x is 20")
    case _:
        print("x is something else")

10.1.2 序列模式匹配

point = (2, 3)
match point:
    case (0, 0):
        print("Origin")
    case (0, y):
        print(f"Point is on the Y axis at {y}")
    case (x, 0):
        print(f"Point is on the X axis at {x}")
    case (x, y):
        print(f"Point is at ({x}, {y})")
    case _:
        print("Not a point")

10.1.3 对象模式匹配

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

p = Point(0, 3)
match p:
    case Point(x=0, y=y):
        print(f"Point is on the Y axis at {y}")
    case Point(x=x, y=0):
        print(f"Point is on the X axis at {x}")
    case Point(x, y):
        print(f"Point is at ({x}, {y})")
    case _:
        print("Not a point")

10.1.4 OR 模式

x = 2
match x:
    case 1 | 2 | 3:
        print("x is 1, 2, or 3")
    case _:
        print("x is something else")

10.1.5 守卫

x = 10
match x:
    case x if x > 5:
        print("x is greater than 5")
    case _:
        print("x is 5 or less")

扩展阅读：Python 3.10里面的Match-Case语法详解