Python 如何选择 NumPy 数组中除索引序列外的所有元素
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How to select all elements in a NumPy array except for a sequence of indices
提问by kilojoules
Say I have some long array and a list of indices. How can I select everything except those indices? I found a solution but it is not elegant:
假设我有一些长数组和一个索引列表。我怎样才能选择除这些索引之外的所有内容？我找到了一个解决方案，但它并不优雅：
import numpy as np
x = np.array([0,10,20,30,40,50,60])
exclude = [1, 3, 5]
print x[list(set(range(len(x))) - set(exclude))]
回答by user2357112 supports Monica
This is what numpy.deletedoes. (It doesn't modify the input array, so you don't have to worry about that.)
这就是numpy.delete它的作用。（它不会修改输入数组，因此您不必担心。）
In [4]: np.delete(x, exclude)
Out[4]: array([ 0, 20, 40, 60])
回答by hpaulj
np.deletedoes various things depending what you give it, but in a case like this it uses a mask like:
np.delete做各种事情取决于你给它什么，但在这种情况下，它使用如下面具：
In [604]: mask = np.ones(x.shape, bool)
In [605]: mask[exclude] = False
In [606]: mask
Out[606]: array([ True, False, True, False, True, False, True], dtype=bool)
In [607]: x[mask]
Out[607]: array([ 0, 20, 40, 60])
回答by Psidom
np.in1dor np.isinto create boolean index based on excludecould be an alternative:
np.in1d或np.isin基于创建布尔索引exclude可能是一种替代方法：
x[~np.isin(np.arange(len(x)), exclude)]
# array([ 0, 20, 40, 60])
x[~np.in1d(np.arange(len(x)), exclude)]
# array([ 0, 20, 40, 60])
回答by percusse
You can also use a list comprehension for the index
您还可以对索引使用列表理解
>>> x[[z for z in range(x.size) if not z in exclude]]
array([ 0, 20, 40, 60])
