Python 如何使用多个索引从 NumPy 数组中获取值
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How to get the values from a NumPy array using multiple indices
提问by user1728853
I have a NumPy array that looks like this:
我有一个 NumPy 数组，如下所示：
arr = np.array([100.10, 200.42, 4.14, 89.00, 34.55, 1.12])
How can I get multiple values from this array by index?
如何通过索引从此数组中获取多个值？
For example, how can I get the values at the index positions 1, 4, and 5?
例如，如何获取索引位置 1、4 和 5 处的值？
I was trying something like this, which is incorrect:
我正在尝试这样的事情，这是不正确的：
arr[1, 4, 5]
采纳答案by bogatron
Try like this:
像这样尝试：
>>> arr = np.array([100.10, 200.42, 4.14, 89.00, 34.55, 1.12])
>>> arr[[1,4,5]]
array([ 200.42, 34.55, 1.12])
And for multidimensional arrays:
对于多维数组：
>>> arr = np.arange(9).reshape(3,3)
>>> arr
array([[0, 1, 2],
[3, 4, 5],
[6, 7, 8]])
>>> arr[[0, 1, 1], [1, 0, 2]]
array([1, 3, 5])
回答by Joran Beasley
you were close
你很接近
>>> print arr[[1,4,5]]
[ 200.42 34.55 1.12]
回答by igo
Another solution is to use np.takeas specified in https://docs.scipy.org/doc/numpy-1.13.0/reference/generated/numpy.take.html
另一种解决方案是np.take按照https://docs.scipy.org/doc/numpy-1.13.0/reference/generated/numpy.take.html 中的规定使用
a = [4, 3, 5, 7, 6, 8]
indices = [0, 1, 4]
np.take(a, indices)
# array([4, 3, 6])
