Quick implement rows, columns, and square

sudoku.py

@@ -4,6 +4,7 @@
 A Sudoku puzzle solver.
 '''
 
+import itertools
 import math
 
 class Sudoku:
@@ -15,21 +16,41 @@ class Sudoku:
         self.size = size
         self.board = bytearray(b'\x00' * (size * size))
 
+    @property
+    def rows(self):
+        sz = self.size
+        return [range(i * sz, i * sz + sz) for i in range(sz)]
+
+    @property
+    def columns(self):
+        sz = self.size
+        sz2 = sz ** 2
+        return [range(i, sz2, sz) for i in range(sz)]
+
     @property
     def solved(self):
         def _check_group(group):
             values = sorted([self.board[i] for i in group])
             is_complete = values == list(range(1, self.size+1))
             return is_complete
-        
+
         sz = self.size
         sz2 = sz ** 2
         dim = int(math.sqrt(self.size))
-
-        rows = [range(i * sz, i * sz + sz) for i in range(sz)]
-        cols = [range(i, sz2, sz) for i in range(sz)]
         # TODO: WIP
 
+    def square(self, x, y):
+        dim = int(math.sqrt(self.size))
+        if (x < 0 or x >= dim) or (y < 0 or y >= dim):
+            raise IndexError('Invalid coordinates for square: ({}, {})'.format(x, y))
+        offset_x = x * dim
+        offset_y = y * dim
+        def _range(i):
+            start = offset_x + i * self.size
+            return range(start, start + dim)
+        ranges = itertools.chain(*[_range(i) for i in range(dim)])
+        return ranges
+
     def __str__(self):
         field_width = len(str(self.size))
         dim = int(math.sqrt(self.size))