On 12 Jul, 07:39, David <davidb...@gmail.com> wrote: > Should the following line work for defining a matrix with zeros? > > c= [[0]*col]*row
No. The rows will be aliased. This will work: c = [[0]*col for i in range(row)] Note that Python lists are not ment to be used as matrices. We have NumPy or the array module for that. > If this a valid way of initializing a matrix in Python 3.2.1, then it > appears to me that a bug surfaces in Python when performing this line: > > c[i][j] = c[i][j] + a[i][k] * b[k][j] > > It writes to the jth column rather than just the i,j cell. That is due to aliasing. > I'm new at Python and am not sure if I'm just doing something wrong if > there is really a bug in Python. The script works fine if I > initialize the matrix with numpy instead: > > c = np.zeros((row,col)) > > So, I know my matrix multiply algorithm is correct (I know I could use > numpy for matrix multiplication, this was just to learn Python). Like so: np.dot(a,b) or ma = np.matrix(a) mb = np.matrix(b) a*b or call BLAS directly: scipy.linalg.fblas.dgemm Sturla -- http://mail.python.org/mailman/listinfo/python-list
