Find the determinant of any 3x3 matrix.

Determinant Finder

def determineMatrix (matrix):
	# here we do some major if statements
	n1 = 0.0
	n2 = 0.0
	size = len(matrix)
	if len(matrix[0]) != size:
		print "Bad matrix for determination. (" + str(len(matrix)) + "x" + str(len(matrix[0])) + ") "
		return 0.0
	else:
		print "determining matrix (" + str(len(matrix)) + "x" + str(len(matrix[0])) + ") "

	# first step here
	for j in range(size):
		n3 = 1
		for i in range(size):
			n = matrixGetNumber(matrix, i, i + j)
			n3 *= n
		n1 += n3
	# second step here
	for j in range(size):
		n3 = 1
		for i in range(size):
			t = (size - 1) - i
			n = matrixGetNumber(matrix, t, i + j)
			n3 *= n
		n2 += n3
	return (n1 - n2)
	
def createMatrix (width, height):
	matrix = list()
	for i in range(height):
		l = list()
		for j in range(width):
			l.append(0)
		matrix.append(l)
	return matrix

def matrixGetNumber (matrix, row, column):
	return matrix[row % len(matrix)][column % len(matrix[0])]

def matrixSetNumber (matrix, row, column, value):
	matrix[row % len(matrix)][column % len(matrix[0])] = value

def readMatrix ():
	matrix = list()
	for i in range(3):
		l = list()
		ms = ""
		print "3x3, enter row " + str(i + 1)
		mstr = raw_input()
		for c in range(len(mstr) + 1):
			mc = ''
			if c == len(mstr):
				mc = ' '
			else: mc = mstr[c:c+1]
			if mc == ' ' or mc == '\t' or mc == '\n':
				l.append(int(ms))
				# print "Append " + ms
				ms = ""
			else:
				ms = ms + mc
		matrix.append(l)
	
	return matrix

matrix = readMatrix()
print "det(matrix) = " + str(determineMatrix(matrix))