np.apply_along_axis slices output when used with ' '.join

Question

.I have a 2D array of strings and I intend to concatenate the strings along each row with a space between them. I used the following code, but it fails with a simple input, but it shouldn't be the case.

import numpy as np

a = np.array([['3', '3', '3', '3', '3', '3', '3', '3', '3', '3', '3', 
               '3','3', '3', '3', '3', '9', '11', '3', '3'],
              ['3', '3', '3', '3', '3', '3', '3', '3', '3', '3', '3', 
               '11', '9', '11', '3', '3', '3', '3', '3', '3']])

def concat(x, separator):
    return separator.join(x).strip()

b = np.apply_along_axis(concat, -1, a, ' ')

Expected:

b = ['3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 9 11 3 3',
     '3 3 3 3 3 3 3 3 3 3 3 11 9 11 3 3 3 3 3 3']

Output (See the end of the 2nd row of b):

b = ['3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 9 11 3 3',
     '3 3 3 3 3 3 3 3 3 3 3 11 9 11 3 3 3 3 3 ']

The last 3 is missing in the output. Any reason why this should happen?

Can I please know the reason of the downvote? – Aman Dalmia Mar 20 '18 at 10:32 — Aman Dalmia, Mar 20 '18 at 10:32

score 0 · Accepted Answer · answered Mar 20 '18 at 10:42

0

What does dtype=object mean while creating a numpy array? to understand why you need to add dtype=object to make it work

answered Mar 20 '18 at 10:42

AdriBento

589
5
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That worked perfectly. Thanks a lot. Learned something new :) – Aman Dalmia Mar 20 '18 at 11:05

np.apply_along_axis slices output when used with ' '.join

1 Answers1