Exercise: Row swap

Task: Consider the following simple python code to interchange rows i and j of a numpy array A.

In [1]:
def swaprow(i, j, A):
    tmp = A[i, :]  
    A[i, :] = A[j, :]
    A[j, :] = tmp     

If there are problems with this (correctness? efficiency? elegance? brevity?), explain them, and produce a better function. (Please do check for correctness before you check anything else.)