Python：如何在某些索引位置获取数组的值？
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Python: How to get values of an array at certain index positions?
提问by MoTSCHIGGE
I have a numpy array like this:
我有一个像这样的 numpy 数组：
a = [0,88,26,3,48,85,65,16,97,83,91]
How can I get the values at certain index positions in ONE step? For example:
如何在一步中获取某些索引位置的值？例如：
ind_pos = [1,5,7]
The result should be:
结果应该是：
[88,85,16]
采纳答案by Padraic Cunningham
Just index using you ind_pos
只是索引使用你 ind_pos
ind_pos = [1,5,7]
print (a[ind_pos])
[88 85 16]
In [55]: a = [0,88,26,3,48,85,65,16,97,83,91]
In [56]: import numpy as np
In [57]: arr = np.array(a)
In [58]: ind_pos = [1,5,7]
In [59]: arr[ind_pos]
Out[59]: array([88, 85, 16])
回答by Ffisegydd
You can use index arrays, simply pass your ind_posas an index argument as below:
您可以使用索引数组，只需将您的ind_pos作为索引参数传递如下：
a = np.array([0,88,26,3,48,85,65,16,97,83,91])
ind_pos = np.array([1,5,7])
print(a[ind_pos])
# [88,85,16]
Index arrays do not necessarily have to be numpy arrays, they can be also be lists or any sequence-like object (though not tuples).
索引数组不一定必须是 numpy 数组，它们也可以是列表或任何类似序列的对象（尽管不是元组）。
回答by user3906621
your code would be
你的代码是
a = [0,88,26,3,48,85,65,16,97,83,91]
a = [0,88,26,3,48,85,65,16,97,83,91]
ind_pos = ind_pos = [a[1],a[5],a[7]]
ind_pos = ind_pos = [a[1],a[5],a[7]]
print ind_pos
print ind_pos
you get [88, 85, 16]
你得到 [88, 85, 16]
回答by chepner
Although you ask about numpyarrays, you can get the same behavior for regular Python lists by using operator.itemgetter.
尽管您询问numpy数组，但您可以通过使用operator.itemgetter.
>>> from operator import itemgetter
>>> a = [0,88,26,3,48,85,65,16,97,83,91]
>>> ind_pos = [1, 5, 7]
>>> print itemgetter(*ind_pos)(a)
(88, 85, 16)
回答by Ohad Cohen
The one liner "no imports" version
单班轮“无进口”版本
a = [0,88,26,3,48,85,65,16,97,83,91]
ind_pos = [1,5,7]
[ a[i] for i in ind_pos ]
