How to make numpy array column sum up to 1

Question

I am working on building a transition matrix for implementing the PageRank algorithm. How could I use numpy to make sure that the columns add up to one.

For example:

Answer 1

for i in range(len(A[0])):
    col_sum = A[:, i].sum()
    if col_sum != 0:
        A[:, i] = A[:, i]/col_sum
    else: 
        pass

The for loop is a bit sloppy and I'm sure there's a much more elegant way but it works.
Replace pass with A[:, i] = 1/len(A[0]) to eliminate dangling nodes and make the matrix column stocastic.