How to efficiently define custom global comparator in Python 3?

Question

I want to define comparator like:

def cmp_smth(x, y):
    if x == y:
        return 0
    elif fn(x, y):
        return -1
    else:
        return 1
comparator = functools.cmp_to_key(cmp_smth)

And it works fine with cmp_to_key converter, ie:

sorted([x, y, z], key=comparator)

But what if I want to sort something more complicated, ie tuples:

sorted([(1, x), (2, y), (3, z)], key=???)

How to use my global comparator in this case?

Answer 1

您可以使用lambda将键函数（以前是比较器）映射到每个元组的第二个元素：

sorted([(1, x), (2, y), (3, z)], key=lambda x: comparator(x[1]))