Python列表理解:测试函数返回 [英] Python list comprehension: test function return

问题描述

有没有一种方法可以测试列表(或字典)理解中的函数返回?我想避免这样写:

Is there a way to test the return of a function in a list (or dict) comprehension? I'd like to avoid writing that:

lst = []
for x in range(10):
  bar = foo(x)
  if bar:
    lst.append(bar)

并使用列表理解.显然，我不想写:

and use a list comprehension instead. Obviously, I don't want to write:

[foo(x) for x in range(10) if foo(x)]

是吗?

[foo(x) for x in range(10) if ??? ]

推荐答案

如何

filter(None, map(foo, range(10)))

如果您不想保留中间列表，请将map()替换为 itertools.ifilter() ，整个事情就可以变成发电机.

If you don't want to keep the intermediate list, replace map() with itertools.imap(). And with itertools.ifilter(), the whole thing could be turned into a generator.

itertools.ifilter(None, itertools.imap(foo, range(10)))

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