Empty Sudoku board, with a pretty printing __str__()

sudoku.py

@@ -0,0 +1,37 @@
+#!env python3
+# Eryn Wells <eryn@erynwells.me>
+'''
+A Sudoku puzzle solver.
+'''
+
+import math
+
+class Sudoku:
+    def __init__(self, size=9):
+        dim = math.sqrt(size)
+        if dim != int(dim):
+            raise ValueError('Board size must have an integral square root.')
+        self.dimension = int(dim)
+        self.size = size
+        self.board = bytearray(b'\x00' * (size * size))
+
+    def __str__(self):
+        field_width = len(str(self.size))
+        dim = int(math.sqrt(self.size))
+        lines = []
+        spacer = '+' + '+'.join(['-' * (field_width * dim) for _ in range(dim)]) + '+'
+        for line in range(self.size):
+            chunks = []
+            for i in range(dim):
+                fields = []
+                for j in range(dim):
+                    idx = line * self.size + i * dim + j
+                    fields.append('{{board[{i}]:^{width}}}'.format(i=idx, width=field_width))
+                chunks.append(''.join(fields))
+            if (line % dim) == 0:
+                lines.append(spacer)
+            lines.append('|' + '|'.join(chunks) + '|')
+        lines.append(spacer)
+        fmt = '\n'.join(lines)
+        out = fmt.format(board=[str(n) if n != 0 else ' ' for n in self.board])
+        return out