Python：如何在某些索引位置获取数组的值？

Question

我有一个像这样的numpy数组：

a = [0,88,26,3,48,85,65,16,97,83,91]

如何在一步中获取某些指数位置的值？例如：

ind_pos = [1,5,7]

结果应为：

[88,85,16]

Answer 1

使用ind_pos

进行索引

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])

Answer 2

一个班轮＆＃34;没有进口＆＃34;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 ]

Answer 3

虽然您询问numpy数组，但使用operator.itemgetter可以获得常规Python列表的相同行为。

>>> 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)

Answer 4

您可以使用index arrays，只需将ind_pos作为索引参数传递，如下所示：

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]

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）。

Answer 5

您的代码将是

a = [0,88,26,3,48,85,65,16,97,83,91]

ind_pos = ind_pos = [a[1],a[5],a[7]]

print ind_pos

你得到[88,85,16]