Concatenation of 2d lists

Question

I have 2 lists of shape [355,1600] and [5,1600]. I wish to concatenate them into a new list of shape [360,1600]. How should I do it?

Answer 1

You should've mentioned it was for numpy arrays. Use np.vstack() to concatenate the arrays vertically (same amount of columns, different amount of rows) or np.hstack() to concatenate them horizontally (same amount of rows, different amount of columns)

import numpy as np

# 2 rows, 3 columns
n1 = np.array([[1,2,3],[4,5,6]])

# 1 row, 3 columns
n2 = np.array([[7,8,9]])

# 1+2==3 rows, 3 columns
n3 = np.vstack((n1,n2))

print(n3)
# [[1 2 3]
# [4 5 6]
# [7 8 9]]

Answer 2

if you meant the result to be [360, 3200]

the you could do this:
li1 = [355, 1600]
li2 = [5, 1600]
li3 = [li1[i] + li2[i] for i in range(len(li1))]

if it's not this, then tell us what the system behind combining the lists is...

Answer 3

# 2 rows, 3 columns
n1 = [[1, 2, 3], [4, 5, 6]]

# 1 row, 3 columns
n2 = [[7, 8, 9]]

# 1+2==3 rows, 3 columns
n3 = n1+n2

print(n3)
# [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

Answer 4

Diego is that true for numpy arrays as well? Just asking.

Answer 5

Diego I wanted it for lists only. But was curious to know about the numpy array as well because I might use it instead of lists.

Thank you! Much appreciated.

Answer 6

Anton Böhler I have mentioned that the new list should be of shape[360,1600]. Thank you.

Answer 7

~ swim ~ Yeah I'll try this. Sounds clear.

I am not trying to perform addition on the lists, just an append like operation.

n1 has 355 rows and n2 has 5 rows.

Now n3 should have 360 rows.

By your comment, I understand the operation of first copying n1 in n3 and then n2 in n3.

Thank you.