Add GameNode.main_line()

README.rst

@@ -271,6 +271,11 @@ Features
       >>> first_game.headers["Black"]
       'Bordais'
 
+      >>> # Get the mainline as a list of moves.
+      >>> moves = first_game.main_line()
+      >>> first_game.board().variation_san(moves)
+      '1. e4 c5 2. c4 Nc6 3. Ne2 Nf6 4. Nbc3 Nb4 5. g3 Nd3#'
+
       >>> # Iterate through the mainline of this embarrasingly short game.
       >>> node = first_game
       >>> while not node.is_end():

chess/pgn.py

@@ -246,6 +246,13 @@ def add_main_variation(self, move, comment=""):
         self.variations.insert(0, node)
         return node
 
+    def main_line(self):
+        """Yields the moves of the main line starting in this node."""
+        node = self
+        while node.variations:
+            node = node.variations[0]
+            yield node.move
+
     def add_line(self, moves, comment="", starting_comment="", nags=()):
         """
         Creates a sequence of child nodes for the given list of moves.
@@ -268,7 +275,6 @@ def add_line(self, moves, comment="", starting_comment="", nags=()):
 
         return node
 
-
     def accept(self, visitor, _board=None):
         """
         Traverse game nodes in PGN order using the given *visitor*. Returns

test.py

@@ -1966,10 +1966,9 @@ def test_add_line(self):
         game = chess.pgn.Game()
         game.add_variation(chess.Move.from_uci("e2e4"))
 
-        tail = game.add_line([
-            chess.Move.from_uci("g1f3"),
-            chess.Move.from_uci("d7d5")
-        ], starting_comment="start", comment="end", nags=(17, 42))
+        moves = [chess.Move.from_uci("g1f3"), chess.Move.from_uci("d7d5")]
+
+        tail = game.add_line(moves, starting_comment="start", comment="end", nags=(17, 42))
 
         self.assertEqual(tail.parent.move, chess.Move.from_uci("g1f3"))
         self.assertEqual(tail.parent.starting_comment, "start")
@@ -1980,6 +1979,14 @@ def test_add_line(self):
         self.assertEqual(tail.comment, "end")
         self.assertTrue(42 in tail.nags)
 
+    def test_main_line(self):
+        moves = [chess.Move.from_uci(uci) for uci in ["d2d3", "g8f6", "e2e4"]]
+
+        game = chess.pgn.Game()
+        game.add_line(moves)
+
+        self.assertEqual(list(game.main_line()), moves)
+
 
 class StockfishTestCase(unittest.TestCase):