case/switch 语句的 Python 等价物是什么?

2022-01-19 00:00:00 python switch-statement case-statement

问题描述

是否有 Python 等效的 case 语句，例如 VB.NET 或 C# 中可用的示例?

Is there a Python equivalent for the case statement such as the examples available in VB.NET or C#?

解决方案

Python 3.10 及以上版本

在 Python 3.10 中，他们引入了模式匹配.

Python 文档中的示例:

def http_error(status):
    match status:
        case 400:
            return "Bad request"
        case 404:
            return "Not found"
        case 418:
            return "I'm a teapot"
        case _:
            return "Something's wrong with the internet"

在 Python 3.10 之前

虽然官方文档很高兴不提供开关，但我看到了一个使用字典的解决方案.

Before Python 3.10

While the official documentation are happy not to provide switch, I have seen a solution using dictionaries.

例如:

# define the function blocks
def zero():
    print "You typed zero.
"

def sqr():
    print "n is a perfect square
"

def even():
    print "n is an even number
"

def prime():
    print "n is a prime number
"

# map the inputs to the function blocks
options = {0 : zero,
           1 : sqr,
           4 : sqr,
           9 : sqr,
           2 : even,
           3 : prime,
           5 : prime,
           7 : prime,
}

然后调用等效的 switch 块:

Then the equivalent switch block is invoked:

options[num]()

如果您严重依赖失败，这将开始崩溃.

This begins to fall apart if you heavily depend on fall through.

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