Lecture Notes 18 Mar 2013

class Matrix (object):
  def __init__ (self, row = 0, col = 0):
    self.row = row
    self.col = col
    self.matrix = []

  # performs a matrix addition
  def __add__ (self, other):
    if (self.row != other.row) or (self.col != other.col):
      return None

    mat = Matrix (self.row, self.col)
    for i in range (self.row): 
      new_row = []
      for j in range (self.col):
        new_row.append (self.matrix[i][j] + other.matrix[i][j])
      mat.matrix.append (new_row)

    return mat

  # performs a matrix multiplication
  def __mul__ (self, other):
    if (self.col != other.row):
      return None

    mat = Matrix (self.row, other.col)
    for i in range (self.row):
      new_row = []
      for j in range (other.col):
        sum = 0
	for k in range (other.row):
	  sum = sum + self.matrix[i][k] * other.matrix[k][j]
	new_row.append(sum)
      mat.matrix.append(new_row)
    return mat

  # returns a string representation of the matrix
  def __str__ (self):
    s = ''
    ...
    return s

# read a file and create a matrix
def readMatrix (inFile):
  line = inFile.readline().rstrip("\n").split()
  row = int (line[0])
  col = int (line[1])

  mat = Matrix (row, col)

  for i in range (row):
    line = inFile.readline().rstrip("\n").split()
    for j in range (col):
      line[j] = int (line[j])
    mat.matrix.append(line)
  line = inFile.readline()

  return mat