Swap zeros in numpy matrix

Question

I have a numpy matrix like so:

array([[2,  1, 23, 32],
       [34, 3, 3, 0],
       [3, 33, 0, 0],
       [32, 0, 0, 0]], dtype=int32)

Now

Answer 1

pandas method:

In [181]:
# construct df from array
df = pd.DataFrame(a)
# call apply and call np.roll rowise and roll by the number of zeroes
df.apply(lambda x: np.roll(x, (x == 0).sum()), axis=1).values

Out[181]:
array([[ 2,  1, 23, 32],
       [ 0, 34,  3,  3],
       [ 0,  0,  3, 33],
       [ 0,  0,  0, 32]])

This uses apply so we can call np.roll on each row by the number of zeroes in each row