How do I import and and export a game in PGN after playing a move?

[Roy-Orbison]

I'm a Python noob, and I don't quite get how the various objects relate. The docs say that game.board() returns a copy, so how then does one push the move Stockfish takes back on to the game's stack?

This is roughly what I have so far:

import chess
import chess.engine
import chess.pgn

engine = chess.engine.SimpleEngine.popen_uci('stockfish')
pgn = '' # may be an empty string when new game, or a game in play, in PGN notation

if pgn == '':
	game = chess.pgn.Game()
	board = game.board()
	# need to set starting colour
else:
	import io

	game = chess.pgn.read_game(io.StringIO(pgn))
	board = game.board()
	for move in game.mainline_moves():
		board.push(move)

result = engine.play(board, chess.engine.Limit(time=2.0))
board.push(result.move)

checkmate = board.is_checkmate()
exporter = chess.pgn.StringExporter(columns=None, headers=False, variations=False, comments=False)
pgn = game.accept(exporter)

[niklasf]

Extend mainline with a single move

To edit a game, you can use methods like GameNode.add_main_variation():

game = chess.pgn.Game()
node = game.end()

result = engine.play(node.board(), chess.engine.Limit(time=2.0))
node = node.add_main_variation(result.move)
# node now again points to the end of the game

Convert to and from board

If the game is completely linear with no side variations, you can also just work with chess.Board only.

board = game.end().board()  # Create board with all moves of an existing game

result = engine.play(node.board(), chess.engine.Limit(time=2.0))
board.push(resul.move)

# ...

print(board.root().variation_san(board.move_stack))  # Print move stack in SAN directly

game = chess.pgn.Game.from_board(board)  # Convert back to game, if needed