concatenate multiple numpy arrays in one array?

Question

Assume I have many numpy array:

a = ([1,2,3,4,5])
b = ([2,3,4,5,6])
c = ([3,4,5,6,7])

and I want to generate a new 2-D array:

d = ([[1,2,3,4,5],[2,3,4,5,6],[3,4,5,6,7]])

What should I code? I tried used:

d = np.concatenate((a,b),axis=0)
d = np.concatenate((d,c),axis=0)

It returns:

d = ([1,2,3,4,5,2,3,4,5,6,3,4,5,6,7])

Answer 1

As mentioned in the comments you could just use the np.array function:

>>> import numpy as np
>>> a = ([1,2,3,4,5])
>>> b = ([2,3,4,5,6])
>>> c = ([3,4,5,6,7])

>>> np.array([a, b, c])
array([[1, 2, 3, 4, 5],
       [2, 3, 4, 5, 6],
       [3, 4, 5, 6, 7]])

In the general case that you want to stack based on a "not-yet-existing" dimension, you can also use np.stack:

>>> np.stack([a, b, c], axis=0)
array([[1, 2, 3, 4, 5],
       [2, 3, 4, 5, 6],
       [3, 4, 5, 6, 7]])

>>> np.stack([a, b, c], axis=1)  # not what you want, this is only to show what is possible
array([[1, 2, 3],
       [2, 3, 4],
       [3, 4, 5],
       [4, 5, 6],
       [5, 6, 7]])