如何在字典理解中使用 if/else? [英] How can I use if/else in a dictionary comprehension?

问题描述

在 Python 2.7+ 中是否存在一种方法来制作如下所示的内容?

Does there exist a way in Python 2.7+ to make something like the following?

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

我知道你可以用'if'做任何事情:

I know you can make anything with just 'if':

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

推荐答案

你已经明白了:A if test else B 是一个有效的 Python 表达式.如图所示，您的 dict 理解的唯一问题是 dict 理解中表达式的位置必须有两个表达式，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() }

最后的 if 子句充当过滤器，这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.

这篇关于如何在字典理解中使用 if/else?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！