为什么对双重切片的numpy数组进行分配不起作用? [英] Why does an assignment for double-sliced numpy arrays not work?

问题描述

为什么以下几行不能按我预期的那样工作?

why do the following lines not work as I expect?

import numpy as np
a = np.array([0,1,2,1,1])
a[a==1][1:] = 3
print a
>>> [0 1 2 1 1]
# I would expect [0 1 2 3 3]

这是虫子"还是有其他推荐的方法?

Is this a 'bug' or is there another recommended way to this?

另一方面，以下工作原理:

On the other hand, the following works:

a[a==1] = 3
print a
>>> [0 3 2 3 3]

干杯，菲利普

推荐答案

看来您根本无法通过像这样的双重切片来完成作业.

It appears you simply can't do an assignment through a double-slice like that.

这可以:

a[numpy.where(a==1)[0][1:]] = 3

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