如何在匹配案例中执行其他（默认）？

Question

Python recently has released match-case in version 3.10。问题是我们如何在 Python 中进行默认情况？我可以 if/elif 但不知道该怎么做。下面是代码：

x = "hello"
match x:
    case "hi":
        print(x)
    case "hey":
        print(x)
    default:
        print("not matched")

这是我自己添加的 default。我想知道在 Python.

中执行此操作的方法

Answer 1

您可以在 Python 中定义默认情况。为此you use a wild card (_)。下面的代码演示了它：

x = "hello"
match x:
    case "hi":
        print(x)
    case "hey":
        print(x)
    case _:
        print("not matched")

Answer 2

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

对比：https://docs.python.org/3.10/whatsnew/3.10.html#syntax-and-operations

Answer 3

for thing in [[1,2],[2,11],[12,14,13],[10],[10,20,30,40,50]]:
match thing:
    case [x]:
        print(f"single value: {x}")
    case [x,y]:
        print(f"two values: {x} and {y}")
    case [x,y,z]:
        print(f"three values: {x}, {y} and {z}")       
    case _: # change this in default 
        print("too many values")

如果您想阅读并获得更多理解：https://towardsdatascience.com/pattern-matching-in-python-3-10-6124ff2079f0

如何在匹配案例中执行其他（默认）？

How to do an else (default) in match-case?

python

python-3.10

structural-pattern-matching