How can I add an additional row and column to an array?

Question

I need to add a column and a row to an existing Numpy array at a defined position.

Answer 1

There are many ways to do this in numpy, but not all of them let you add the row/column to the target array at any location (e.g., append only allows addition after the last row/column). If you want a single method/function to append either a row or column at any position in a target array, i would go with 'insert':

T = NP.random.randint(0, 10, 20).reshape(5, 4)
c = NP.random.randint(0, 10, 5)
r = NP.random.randint(0, 10, 4)
# add a column to T, at the front:
NP.insert(T, 0, c, axis=1)
# add a column to T, at the end:
NP.insert(T, 4, c, axis=1)
# add a row to T between the first two rows:
NP.insert(T, 2, r, axis=0)