Added move method and supporting methods

chess.py

@@ -48,6 +48,8 @@ class Piece:
 class Game:
     def __init__(self):
         self.make_board()
+        self.moves = []
+        self.stack = []
 
     def __repr__(self):
         # Unicode board representation
@@ -84,6 +86,23 @@ class Game:
     def occupying(self, piece):
         return [sq for sq in squares if self.board[sq] == piece]
 
+    def move(self, source, target):
+        if not self.is_legal(source, target):
+            return False
+        board = self.board
+        moved = board[source]
+        eaten = board[target]
+
+        self.moves.append((source, target))
+        self.stack.append(eaten)
+
+        board[source] = Piece()
+        board[target] = moved
+        return True
+
+    def is_legal(self, source, target):
+        return target in self.possible_moves(source)
+
     def is_attacked(self, sq):
         return False
 
@@ -159,6 +178,7 @@ class Game:
             vecs = product([-1, 0, 1], [-1, 0, 1])
             return [sq for sq in addvs(sq, vecs)
                        if is_possible(sq) and not self.is_attacked(sq)]
+        return []
 
 
 
@@ -166,8 +186,9 @@ def test():
     game = Game()
     assert len(squares) == 8**2
     assert sum(map(len, init_positions.values())) == 8*4
-    game.board["d3"] = Piece("black", "queen")
+    moves = [("a2", "a3"), ("b1", "c3"), ("d1", "d2")]
+    for m in moves:
+        game.move(*m)
         print (game)
-    print (game.possible_moves("d2"))
 
 test()