Python：if / else in dict的理解？ [英] Python: if/else in dict comprehension?

问题描述

在python2.7 +存在任何方式来做如下：

In python2.7+ exist any way to make something like:

{ something_if_true if condition else something_if_false for key, value in dict_.items() }

我知道你可以做任何事情只是'if'

I know you can make anything with just 'if'

{ something_if_true for key, value in dict_.items() if condition}

推荐答案

你已经得到它： A如果测试其他B 是一个有效的python表达式。你的dict理解的唯一问题是，在一个字母理解中表达的地方必须有两个表达式，用冒号分隔：

You've already got it: A if test else B is a valid python expression. The only problem with your dict comprehension as shown is that the place for an expression in a dict comprehension must have two expressions, separated by a colon:

{ (some_key if condition else default_key):(something_if_true if condition 
          else something_if_false) for key, value in dict_.items() }

最终 if 子句作为过滤器，与具有条件表达式不同

The final if clause acts as a filter, which is different from having the conditional expression.

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