Simulate the "fill color" operation of programs like MS with lists.

paint.py

'''
' paint.py
'
' Simulate the "fill color" operation of
' programs like MS with lists.
'
' Will Badart
' SEP 2016
'
'''

def paint(matrix, color, x, y):

    current_color = matrix[x][y]
    matrix[x][y] = color

    if x - 1 >= 0 and matrix[x - 1][y] == current_color:
        paint(matrix, color, x - 1, y)
    if x + 1 < len(matrix) and matrix[x + 1][y] == current_color:
        paint(matrix, color, x + 1, y)
    if y - 1 >= 0 and matrix[x][y - 1] == current_color:
        paint(matrix, color, x, y - 1)
    if y + 1 < len(matrix[x]) and matrix[x][y + 1] == current_color:
        paint(matrix, color, x, y + 1)

canvas = [[1, 1, 1, 1, 1],
          [1, 2, 1, 1, 2],
          [1, 2, 2, 1, 1],
          [1, 1, 1, 1, 1]]

def print2d(matrix):
    for row in matrix:
        print row

print 'Original canvas:'
print2d(canvas)

paint(canvas, 3, 1, 1)

print 'Painted canvas:'
print2d(canvas)