在使用 Python 的设置差异时保留顺序

2022-01-17 00:00:00 python set

问题描述

我正在 Python 中进行集差操作:

I'm doing a set difference operation in Python:

x = [1, 5, 3, 4]
y = [3]

result = list(set(x) - set(y))
print(result)

我明白了:

[1, 4, 5]

如您所见，列表元素的顺序发生了变化.如何以原始格式保留列表 x?

As you can see, the order of the list elements has changed. How can I retain the list x in original format?

解决方案

看起来你需要一个有序集合而不是常规集合.

It looks like you need an ordered set instead of a regular set.

>>> x = [1, 5, 3, 4]
>>> y = [3]
>>> print(list(OrderedSet(x) - OrderedSet(y)))
[1, 5, 4]

Python 没有有序集，但很容易制作:

Python doesn't come with an ordered set, but it is easy to make one:

import collections

class OrderedSet(collections.Set):
    def __init__(self, iterable=()):
        self.d = collections.OrderedDict.fromkeys(iterable)

    def __len__(self):
        return len(self.d)

    def __contains__(self, element):
        return element in self.d

    def __iter__(self):
        return iter(self.d)

希望这会有所帮助:-)

Hope this helps :-)

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