使用比较器功能进行排序 [英] Using a comparator function to sort

问题描述

因此，我正在使用一些预先存在的比较器，它们比较两个元组中的某些值，如果第一个大于第二个，则返回true，否则返回false.这是其中之一的代码:

So I'm working with a few pre-existing comparators that compare certain values in two tuples and return true if the first is greater than the second, false if otherwise. Here's the code for one of them:

def cmpValue(subInfo1, subInfo2):
    """
    Returns True if value in (value, work) tuple subInfo1 is GREATER than
    value in (value, work) tuple in subInfo2
    """
    # TODO...
    if subInfo1[0] > subInfo2[0]:
        return True
    else:
        return False

现在，我有一个字典，其中包含许多上面比较类型的元组条目.我想按相反的顺序对它们进行排序，但是我不太了解如何实现.我在想类似的东西:

Now, I have a dictionary that has numerous tuple entries of the type being compared above. I want to sort them all in reverse order, but I don't really understand how I would accomplish that. I was thinking something like:

sortedDict = sorted(subjects, key=comparator, reverse = True)

但是我不知道将什么传递给比较器，因为每个比较器都带有两个参数(subInfo1，subInfo2). 我无法更改比较器功能.

But I don't know what to pass into the comparator because each comparator takes two arguments (subInfo1, subInfo2). I cannot change the comparator functions.

推荐答案

您将比较器作为key函数传递.您应该将其作为cmp传递，并包装在某种将其转换为适当比较器的函数中.

You're passing the comparator as the key function. You should be passing it as the cmp, wrapped in some kind of function that turns it into a proper comparator.

def make_comparator(less_than):
    def compare(x, y):
        if less_than(x, y):
            return -1
        elif less_than(y, x):
            return 1
        else:
            return 0
    return compare

sortedDict = sorted(subjects, cmp=make_comparator(cmpValue), reverse=True)

(尽管实际上，您应该使用关键功能:

(Although actually, you should be using key functions:

sorted(subjects, operator.itemgetter(0), reverse=True)

还要注意，sortedDict实际上不是dict，因此名称相当混乱.)

Also note that sortedDict will not actually be a dict, so the name is rather confusing.)

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