add to numpy string array

Question

I have the following two numpy arrays:

a1
array(['T', 'T', 'T', ..., 'G', 'A', 'A'], dtype=object)

a2
array(['A', 'G', 'C', ..., 'A', 'T', 'G'], dtype=object)

I want to add each element from the two arrays. The following command works:

s = a1 + a2
s
array(['TA', 'TG', 'TC', ..., 'GA', 'AT', 'AG'], dtype=object)

But I get an error when trying to use numpy.char.add:

np.char.add(a1, a2)

TypeError: string operation on non-string array

Why does this happen?

if you don't want to use numpy.char.add, you can either use a classic for loop and zip, or use the map function. — Reda Drissi
– Reda Drissi, Commented Jul 22, 2019 at 12:05
np.add(a1,a2) works the same as a1+a2. This uses the add method of each object. np.char functions apply string methods to numpy char dtypes. The result is similar — hpaulj
– hpaulj, Commented Jul 22, 2019 at 15:18

Reda Drissi · Accepted Answer · 2019-07-22 11:52:20Z

5

Your types are object try setting it to str and it'll work:

import numpy as np

a1=np.array(['T', 'T', 'T', ..., 'G', 'A', 'A'], dtype=str)

a2=np.array(['A', 'G', 'C', ..., 'A', 'T', 'G'], dtype=str)

print(np.char.add(a1, a2))

answered Jul 22, 2019 at 11:52

Reda Drissi

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Comments

Community · Accepted Answer · 2020-06-20 09:12:55Z

0

If you don't want to change your dataType use zip

print np.asarray([x[0]+x[1] for x in zip(a1,a2)])

Change your datatypes to str and use

print np.char.add(a1, a2)

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Jul 22, 2019 at 12:02

Hima

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