# First Exercise

def change(source,x,y):
# @param source: Picture
# @param x and y: int

 if getWidth(source) != getHeight(source) or x < 0 or y < 0 or x >= getWidth(source) or y >= getHeight(source):
  repaint(source)

 else:

  for i in range(getWidth(source)):
   pixel = getPixel(source,i,y)
   pixelSec = getPixel(source,x,i)
   setColor(pixelSec,getColor(pixel))
   setColor(pixel,getColor(pixelSec))
  repaint (source)

# Second Exercise

def change_matrix(matrix, x, y):
# @param matrix: matrix
# @param x and y: int
# return matrix

 if x < 0 or y < 0 or x > len(matrix)-1 or y > len(matrix[c])-1:
  return matrix

 for count in range(len(matrix)):
  if len(matrix[count]) != len(matrix):
   return matrix

  else:

   for i in range(len(matrix[x])):
    row = matrix[x][i]
    matrix[x][i] = matrix[i][y]
    matrix[i][y] = row
   return matrix