包含两个条件的列表中的最大值 [英] Max in a list with two conditions

问题描述

我在Python中有一个列表，其中每个元素都是这样的元组:

I have a list in Python in which each element is a tuple like this:

(attr1, attr2, attr3)

我想找到具有最大attr2但具有attr3 >= 100的元组.

I want to find the tuple that has the largest attr2, but that have attr3 >= 100.

什么是pythonic方法?

What is the pythonic approach to this?

推荐答案

必须同时过滤并使用key自变量作为max:

You have to both filter and use a key argument to max:

from operator import itemgetter

max(filter(lambda a: a[2] >= 100, yourlist), key=itemgetter(1))

过滤器也可以表示为生成器表达式:

The filter can also be expressed as a generator expression:

max((t for t in yourlist if t[2] >= 100), key=itemgetter(1))

演示:

>>> yourlist = [(1, 2, 300), (2, 3, 400), (3, 6, 50)]
>>> max((t for t in yourlist if t[2] >= 100), key=itemgetter(1))
(2, 3, 400)
>>> max(filter(lambda a: a[2] >= 100, yourlist), key=itemgetter(1))
(2, 3, 400)

请注意，由于您进行了过滤，因此很容易以一个空列表来选择最大值，因此除非您需要该异常沿调用堆栈向上传播，否则您可能需要捕获ValueError s:

Note that because you filter, it's easy to end up with an empty list to pick the max from, so you may need to catch ValueErrors unless you need that exception to propagate up the call stack:

try:
    return max(filter(lambda a: a[2] >= 100, yourlist), key=itemgetter(1))
except ValueError:
    # Return a default
    return (0, 0, 0)

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