matrix.py

class Matrix():
    def __init__(self, width, height):
        self.width = width
        self.height = height
        
        # Initialise the matrix grid
        self.matrix = []
        for row in range(height):
            self.matrix.append([])
            for column in range(width):
                self.matrix[row].append(0)

    def getValue(self, column, row):
        if column >= 0 and column < self.width and row >= 0 and row < self.height:
            return self.matrix[row][column]
        else:
            return None

    def setValue(self, column, row, value):
        self.matrix[row][column] = value

    def addWithMatrix(self, matrix):
        if self.width == matrix.width and self.height == matrix.height:
            for row in range(self.height):
                for column in range(self.width):
                    valueNew = self.getValue(column, row) + matrix.getValue(column, row)
                    self.setValue(column, row, valueNew)
        else:
            print "Error: matrix size must be the same!"

matrixA = Matrix(10, 10)
matrixB = Matrix(11, 10)

matrixA.setValue(1, 2, 5)
matrixB.setValue(1, 2, 6)

matrixA.addWithMatrix(matrixB)

print matrixA.getValue(1, 2)