Reconstruct numpy array using indexing

Question

I have a numpy array of 3*k elements, where k is an integer. For instance, for k=3 I have the array A. Below, x, y, and z are filled by drawing elements from A as shown in the following example:

import numpy as np

A = np.arange(9)
>> array([0, 1, 2, 3, 4, 5, 6, 7, 8])

x = A[0::3]
>> array([0, 3, 6])

y = A[1::3]
array([1, 4, 7])

z = A[2::3]
>> array([2, 5, 8])

Now, I want to use x, y, and z so as to reconstruct A. Is there any convenient way of doing this without using for loops?

score 1 · Accepted Answer · answered Jun 24 '18 at 19:19

1

You can do

np.array([x,y,z]).T.reshape(-1)

answered Jun 24 '18 at 19:19

Umang Gupta

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1

It works like a charm! Many thanks. – nullgeppetto Jun 24 '18 at 19:21
Feel free to accept the answer..if you like :) – Umang Gupta Jun 24 '18 at 19:21
Sure, but you answered too quickly... So you need to wait 5 more minutes :) – nullgeppetto Jun 24 '18 at 19:23
oh sorry! Didnt know that. One more thing, can you check for some other value of k (other than 3) – Umang Gupta Jun 24 '18 at 19:25
1

Yeah, it seems that it works for any integer k. – nullgeppetto Jun 24 '18 at 19:32

Reconstruct numpy array using indexing

1 Answers1