old_contents: #!/usr/bin/env python3
  # -*- coding: utf-8 -*-
  
  def get_columns(rows):
      for row in rows:
          for i in range(0, 8):
              columns[i].append(row[i])
  
  rows = [[], [], [], [], [], [], [], [], []]
  columns = [[], [], [], [], [], [], [], [], []]
  rows[0] = [0, 0, 0, 2, 6, 0, 7, 0, 1]
  rows[1] = [6, 8, 0, 0, 7, 0, 0, 9, 0]
  rows[2] = [1, 9, 0, 0, 0, 4, 5, 0, 0]
  rows[3] = [8, 2, 0, 1, 0, 0, 0, 4, 0]
  rows[4] = [0, 0, 4, 6, 0, 2, 9, 0, 0]
  rows[5] = [0, 5, 0, 0, 0, 3, 0, 2, 8]
  rows[6] = [0, 0, 9, 3, 0, 0, 0, 7, 4]
  rows[7] = [0, 4, 0, 0, 5, 0, 0, 3, 6]
  rows[8] = [7, 0, 3, 0, 1, 8, 0, 0, 0]
  
new_contents: #!/usr/bin/env python3
  # -*- coding: utf-8 -*-
  
  def get_columns(rows):
      for row in rows:
          for i in range(0, 8):
              columns[i].append(row[i])
  
  def get_squares(rows):
      for i in range(0, 8):
          for j in range(0, 3):
              for k in range(0, 3):
                  squares[i].append(rows[j][k])
  
  rows = [[], [], [], [], [], [], [], [], []]
  columns = [[], [], [], [], [], [], [], [], []]
  squares = [[], [], [], [], [], [], [], [], []]
  rows[0] = [0, 0, 0, 2, 6, 0, 7, 0, 1]
  rows[1] = [6, 8, 0, 0, 7, 0, 0, 9, 0]
  rows[2] = [1, 9, 0, 0, 0, 4, 5, 0, 0]
  rows[3] = [8, 2, 0, 1, 0, 0, 0, 4, 0]
  rows[4] = [0, 0, 4, 6, 0, 2, 9, 0, 0]
  rows[5] = [0, 5, 0, 0, 0, 3, 0, 2, 8]
  rows[6] = [0, 0, 9, 3, 0, 0, 0, 7, 4]
  rows[7] = [0, 4, 0, 0, 5, 0, 0, 3, 6]
  rows[8] = [7, 0, 3, 0, 1, 8, 0, 0, 0]
  
subject: Add squares functionality