从列表中获取第一个非None值 [英] Getting the first non None value from list

问题描述

给出一个列表，有没有办法获得第一个非值?而且，如果是这样，这样做的pythonic方式是什么?

Given a list, is there a way to get the first non-None value? And, if so, what would be the pythonic way to do so?

例如，我有:

• a = objA.addreses.country.code
• b = objB.country.code
• c = None
• d = 'CA'

• a = objA.addreses.country.code
• b = objB.country.code
• c = None
• d = 'CA'

在这种情况下，如果a为None，那么我想得到b.如果a和b都为None，我想得到d.

In this case, if a is None, then I would like to get b. If a and b are both None, the I would like to get d.

当前我正在按照(((a or b) or c) or d)的方式进行操作，还有另一种方法吗?

Currently I am doing something along the lines of (((a or b) or c) or d), is there another way?

推荐答案

您可以使用 next() :

You can use next():

>>> a = [None, None, None, 1, 2, 3, 4, 5]
>>> next(item for item in a if item is not None)
1

如果列表仅包含None，它将抛出StopIteration异常.如果要在这种情况下使用默认值，请执行以下操作:

If the list contains only Nones, it will throw StopIteration exception. If you want to have a default value in this case, do this:

>>> a = [None, None, None]
>>> next((item for item in a if item is not None), 'All are Nones')
All are Nones

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