Concatenating two numpy arrays side by side

Question

I need to concatenate two numpy arrays side by side

np1=np.array([1,2,3])
np2=np.array([4,5,6])

I need np3 as [1,2,3,4,5,6] with the same shape, how to achieve this?

[np.concatenate](https://numpy.org/doc/stable/reference/generated/numpy.concatenate.html) works. — ssp, Jul 23 '20 at 03:18
Does this answer your question? [Concatenating two one-dimensional NumPy arrays](https://stackoverflow.com/questions/9236926/concatenating-two-one-dimensional-numpy-arrays) — Bedir Yilmaz, Jul 23 '20 at 04:01

score 2 · Accepted Answer · answered Jul 23 '20 at 03:21

2

In concatenate you have to pass axis as None

In [9]: np1=np.array([1,2,3])
   ...: np2=np.array([4,5,6])

In [10]: np.concatenate((np1,np2), axis=None)
Out[10]: array([1, 2, 3, 4, 5, 6])

answered Jul 23 '20 at 03:21

bigbounty

I suggest to set axis to "1" for safety, imagine the case you did it on array of 2 or more row – Jonathan Roy Feb 15 '23 at 20:27

score 0 · Answer 2 · answered Jul 23 '20 at 03:32

0

Use np.hstack made for this:

np3 = np.hstack((np1,np2))

output:

[1 2 3 4 5 6]

answered Jul 23 '20 at 03:32

Ehsan

2 Answers2