How to append np.array?

February 6, 2022

I have an np.array d1 of (3,6), and an np.array a4 of (1,6).

How can I combine the two np.arrays to form an np.array d2 of (4,6)?

My code is as follows:

import numpy as np
a1=np.array(range(6))
a2=a1+2
a3=a2+3
a4=a3+4
d1=np.array([a1,a2,a3])
d1.shape

Out[44]: (3, 6)

d2=np.array([a1,a2,a3,a4])
d2.shape
d2

Out[45]: (4, 6)
Out[46]: 
array([[ 0,  1,  2,  3,  4,  5],
       [ 2,  3,  4,  5,  6,  7],
       [ 5,  6,  7,  8,  9, 10],
       [ 9, 10, 11, 12, 13, 14]])

How to get d2 from d1 and a4?

I tried np.insert and np.append, but maybe my usage is wrong and I didn’t get the correct result.

>Solution :

I believe https://numpy.org/doc/stable/reference/generated/numpy.concatenate.html concatenate is the command you are looking for.

foo = np.array([[1,2,3],
                [4,5,6]])
bar = np.array([7,8,9])

# axis 0 will combine rows, axis 1 will combine columns
foobar = numpy.concatenate(foo,bar,axis = 0)

array([[1,2,3],
       [4,5,6],
       [7,8,9]])