Insert 1D NumPy array as column in existing 2D array

Question

I have a 2D NumPy array:

>>> import numpy as np
>>> a = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]])
>>> a
array([[1, 2, 3],
       [4, 5, 6],
       [7, 8, 9]])

and a 1D array:

>>> b = np.arange(3)
>>> b
array([0, 1, 2])

Is there an elegant way to insert b into a as a new first column?

So that:

>>> a
array([[0, 1, 2, 3],
       [1, 4, 5, 6],
       [2, 7, 8, 9]])

Zero · Accepted Answer · 2015-04-27 10:12:00Z

2

You could use column_stack()

In [256]: np.column_stack((b, a))
Out[256]:
array([[0, 1, 2, 3],
       [1, 4, 5, 6],
       [2, 7, 8, 9]])

answered Apr 27, 2015 at 10:12

Zero

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