Create matrix

Create matrix of None

A = [[ None for _ in xrange(M)] for _ in xrange(N)]

Create matrix of random numbers

import random
A = [[ random.random() for _ in xrange(M)] for _ in xrange(N)]

Generator for lists of M random elements

import random
A = ([ random.random() for _ in xrange(M)] for _ in iter(int, 1))
for i in A:
    print i
    sleep(0.2)