如何用自定义谓词实现python的any（）？ [英] How to achieve python's any() with a custom predicate?

问题描述

>>> l = list(range(10))
>>> l
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> if filter(lambda x: x > 10, l):
...     print "foo"
... else:                     # the list will be empty, so bar will be printed
...     print "bar"
... 
bar

d喜欢使用 any（） 换而言之，但 any（）只有一个参数：可迭代。有没有更好的方法？

I'd like to use any() for this instead, but any() only takes one argument: the iterable. Is there a better way?

推荐答案

使用 generator expression 作为那一个参数：

Use a generator expression as that one argument:

any(x > 10 for x in l)

这里谓词在表达式的一边生成器表达式，但您可以使用任何表达式，包括使用函数。

Here the predicate is in the expression side of the generator expression, but you can use any expression there, including using functions.

演示：

Demo:

>>> l = range(10)
>>> any(x > 10 for x in l)
False
>>> l = range(20)
>>> any(x > 10 for x in l)
True

生成器表达式将通过遍历 any（）找到 True 结果， p>

The generator expression will be iterated over until any() finds a True result, and no further:

>>> from itertools import count
>>> endless_counter = count()
>>> any(x > 10 for x in endless_counter)
True
>>> # endless_counter last yielded 11, the first value over 10:
...
>>> next(endless_counter)
12

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