在 Python 中切换 [英] Switch in Python

问题描述

我尝试在 python 中创建一个类似 switch 的语句，而不是有很多 if 语句.

I have tried making a switch like statement in python, instead of having a lot of if statements.

代码如下:

def findStuff(cds):
    L=[]
    c=0
    for i in range(0, len(cds), 3):
        a=differencesTo(cds[i:i+3])
        result = {
            a[2][0]==1: c=i+1,
            a[2][1]==1: c=i+2,
            a[2][2]==1: c=i+3,
            a[1]==1: L.append((cds[i:i+3], a[0], c))
        } 
    return L

我的问题是，这不起作用.(适用于 if 语句，但在我看来这会更漂亮).

My problem is, that this does not work. (Works with if statements, but this would in my opinion be more pretty).

我在 Python 中找到了一些开关示例，它们都遵循这种结构.有人可以帮我吗?

I have found some examples of switches in Python, and they follow this structure. Can anyone help me?

推荐答案

(a) 我看不出 if...elif...else 有什么问题

(a) I fail to see what is wrong with if...elif...else

(b) 我假设 python 没有 switch 语句，原因与 Smalltalk 没有的相同:它几乎完全是多余的，如果你想打开类型，你可以添加一个适当的方法你的课；同样，打开值应该在很大程度上是多余的.

(b) I assume that python does not have a switch statement for the same reason that Smalltalk doesn't: it's almost completely redundant, and in the case where you want to switch on types, you can add an appropriate method to your classes; and likewise switching on values should be largely redundant.

注意:我在评论中获悉，无论 Guido 最初没有创建 switch 的原因是什么，添加它的 PEP 都被拒绝了，因为支持添加这样的声明是极其有限.请参阅:http://www.python.org/dev/peps/pep-3103/

Note: I am informed in the comments that whatever Guido's reason for not creating a switch in the first place, PEPs to have it added were rejected on the basis that support for adding such a statement is extremely limited. See: http://www.python.org/dev/peps/pep-3103/

(c) 如果您确实需要切换行为，请使用哈希表 (dict) 来存储可调用对象.结构为:

(c) If you really need switching behaviour, use a hashtable (dict) to store callables. The structure is:

switch_dict = {
    Foo: self.doFoo,
    Bar: self.doBar,
    }

func = switch_dict[switch_var]
result = func() # or if they take args, pass args

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