numpy的唯一，没有排序 [英] numpy unique without sort

问题描述

如何使用numpy unique而不对结果进行排序，而仅按它们在序列中出现的顺序排序?像这样吗?

How can I use numpy unique without sorting the result but just in the order they appear in the sequence? Something like this?

a = [4,2,1,3,1,2,3,4]

np.unique(a) = [4,2,1,3]

而不是

np.unique(a) = [1,2,3,4]

使用朴素的解决方案应该可以编写一个简单的函数.但是，由于我需要多次执行此操作，所以有什么快速而整洁的方法吗?

Use naive solution should be fine to write a simple function. But as I need to do this multiple times, are there any fast and neat way to do this?

推荐答案

您可以使用return_index参数执行此操作:

You can do this with the return_index parameter:

>>> import numpy as np
>>> a = [4,2,1,3,1,2,3,4]
>>> np.unique(a)
array([1, 2, 3, 4])
>>> indexes = np.unique(a, return_index=True)[1]
>>> [a[index] for index in sorted(indexes)]
[4, 2, 1, 3]

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