python - 在字典switch语句中模拟'else' [英] python - Simulating 'else' in dictionary switch statements

问题描述

我正在开发一个使用 if，Elif，Elif，... Else 结构的项目，后来我为类似交换的语句更改了结构，如此处和这里。

I'm working on a project which used a load of If, Elif, Elif, ...Else structures, which I later changed for switch-like statements, as shown here and here.

我将如何添加一个通用的嘿，该选项不存在的情况类似于中的Else，如果，Elif，Else 语句 - 执行的内容如果没有如果或 Elif s可以运行？

How would I go about adding a general "Hey, that option doesn't exist" case similar to an Else in an If, Elif, Else statement - something that gets executed if none of the Ifs or Elifs get to run?

推荐答案

您可以捕获 KeyError 错误，该错误会在地图中找不到值时发生，并返回或处理默认值。例如，使用 n = 3 这段代码：

You could catch the KeyError error that ensues when a value is not found in the map, and return or process there a default value. For example, with n = 3 this piece of code:

if n == 1:
    print 'one'
elif n == 2:
    print 'two'
else:
    print 'too big!'

成为：

choices = {1:'one', 2:'two'}
try:
    print choices[n]
except KeyError:
    print 'too big!'

无论哪种方式，'太大了！'在控制台上打印出来。

Either way, 'too big!' gets printed on the console.

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