如何缩进Python列表推导？ [英] How to indent Python list-comprehensions?

问题描述

列表推导在某些情况下可能很有用，但是它们也可能相当可怕。作为一个稍微夸张的例子，你将如何缩进以下内容？

List comprehensions can be useful in certain situations, but they can also be rather horrible to read.. As a slightly exaggerated example, how would you indent the following?

allUuids = [x.id for x in self.db.query(schema.allPostsUuid).execute(timeout = 20) if x.type == "post" and x.deleted is not False]

推荐答案

我倾向于这样构造它们：

It depends on how long they are. I tend to structure them like so:

[x.id for x
 in self.db.query(schema.allPostsUuid).execute(timeout=20)
 if x.type == 'post' 
    and x.deleted is not False
    and ...
    and ...]

这样每个表达式都有自己的行。

That way every expression has its own line.

如果任何行变得太大，我喜欢在lambda或表达式中提取它：

If any line becomes too big I like to extract it out in a lambda or expression:

transform = lambda x: x.id
results = self.db.query(schema.allPostsUuid).execute(timeout=20)
condition = lambda x: x.deleted is not False and ... and ...
[transform(x) for x in results if condition(x)]

如果lambda变得太长，它会被提升为一个函数。

And then if a lambda becomes too long it gets promoted to a function.

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