如何同时选择数组的所有奇数行和所有偶数列 [英] How can I simultaneously select all odd rows and all even columns of an array

问题描述

我是编程新手，我需要一个程序，该程序可以在一个代码中同时选择Numpy数组的所有奇数行和所有偶数列. 这是我尝试过的:

I'm new to programming and I need a program, that can select all odd rows and all even columns of a Numpy array at the same time in one code. here is what I tried:

>In [78]: a

>Out[78]:
>array([[ 1,  2,  3,  4,  5],
>       [ 6,  7,  8,  9, 10],
>       [11, 12, 13, 14, 15],
>       [16, 17, 18, 19, 20]])
>
>In [79]: for value in range(a.shape[0]):
>     if value %2 == 0:
>        print a[value,:]

>[1 2 3 4 5]
>[11 12 13 14 15]
>
>In [82]: for value in range(a.shape[1]):
>    if value %2 == 1:
>        print a[:,value]

>[ 2  7 12 17]
>[ 4  9 14 19]

我用(: even)读过一些东西，但不知道我可以用哪种方式使用它. 感谢您的帮助.

I've read something with (: even) but don't know in which way I could use it. Thanks for your Help.

Han

推荐答案

假设您有这个数组x:

>>> import numpy
>>> x = numpy.array([[ 1,  2,  3,  4,  5],
... [ 6,  7,  8,  9, 10],
... [11, 12, 13, 14, 15],
... [16, 17, 18, 19, 20]])

要获取其他所有奇数行，就像您上面提到的那样:

To get every other odd row, like you mentioned above:

>>> x[::2]
array([[ 1,  2,  3,  4,  5],
       [11, 12, 13, 14, 15]])

要获取其他偶数列，就像您上面提到的那样:

To get every other even column, like you mentioned above:

>>> x[:, 1::2]
array([[ 2,  4],
       [ 7,  9],
       [12, 14],
       [17, 19]])

然后，将它们组合在一起将产生:

Then, combining them together yields:

>>> x[::2, 1::2]
array([[ 2,  4],
       [12, 14]])

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