How we Concatenate Two spitted array

Question

Let say we have array x

x = np.array([1, 2, 3, 99, 99, 3, 2, 1])
x1, x2, x3 = np.split(x, [3, 6])

I want to use append this two splited array let say x1 and x2 I want to Concatenate like [1, 2, 3, 2, 1] If I am using for Concatenate

x4 = x1+x3
x4

We are getting error like ValueError: operands could not be broadcast together with shapes (3,) (2,)

What we can do for Concatenation two splited array . can you please help me with this

score 0 · Answer 1 · answered Mar 15 '20 at 10:57

You might use np.hstack to get desired result:

import numpy as np
x = np.array([1, 2, 3, 99, 99, 3, 2, 1])
x1, x2, x3 = np.split(x, [3, 6])
x4 = np.hstack((x1, x3))
print(x4)  # [1 2 3 2 1]

hstack stands for horizontal stack, there also exist vstack for vertical stack, these functions can be also used with multidimensional arrays.

score -1 · Accepted Answer · answered Mar 15 '20 at 10:39

-1

+ is element-wise addition for numpy arrays. I guess you are looking for np.concatenate.

>>> np.concatenate([x1, x2])                                                    
array([ 1,  2,  3, 99, 99])

answered Mar 15 '20 at 10:39

timgeb

Thank you so much .. like wise if we are discard/subtract bigger array with smaller array then what we can do for this situation example [1, 2, 3, 4, 5] - [4,5] = [1,2,3,4] , what we can do for this – John Golzio Mar 15 '20 at 10:53
@LalatenduJena why is there a `4` in the result? – timgeb Mar 16 '20 at 04:07
yes sorry for typing mistake it'ts [1,2,3] only – John Golzio Mar 16 '20 at 10:03
@LalatenduJena there's no builtin function to do that, you'd have to write some custom logic. – timgeb Mar 16 '20 at 19:33
Ok thanks for your response .... I will try to write built in function for this – John Golzio Mar 18 '20 at 12:22

2 Answers2