PGN parsing and writing

Game model

Games are represented as a tree of moves. Each GameNode can have extra information such as comments. The root node of a game (Game extends GameNode) also holds general information, such as game headers.

class chess.pgn.Game

The root node of a game with extra information such as headers and the starting position.

By default the following 7 headers are provided in an ordered dictionary:

>>> game = chess.pgn.Game()
>>> game.headers["Event"]
>>> game.headers["Site"]
>>> game.headers["Date"]
>>> game.headers["Round"]
>>> game.headers["White"]
>>> game.headers["Black"]
>>> game.headers["Result"]

Also has all the other properties and methods of GameNode.


A collections.OrderedDict() of game headers.


A list of illegal or ambiguous move errors encountered while parsing the game.


Gets the starting position of the game.

Unless the SetUp and FEN header tags are set this is the default starting position.


Setup a specific starting position. This sets (or resets) the SetUp, FEN and Variant header tags.

class chess.pgn.GameNode

The parent node or None if this is the root node of the game.


The move leading to this node or None if this is the root node of the game.

nags = set()

A set of NAGs as integers. NAGs always go behind a move, so the root node of the game can have none.

comment = ''

A comment that goes behind the move leading to this node. Comments that occur before any move are assigned to the root node.

starting_comment = ''

A comment for the start of a variation. Only nodes that actually start a variation (starts_variation()) can have a starting comment. The root node can not have a starting comment.


A list of child nodes.


Gets a board with the position of the node.

It’s a copy, so modifying the board will not alter the game.


Gets the standard algebraic notation of the move leading to this node.

Do not call this on the root node.


Gets the root node, i.e. the game.


Follows the main variation to the end and returns the last node.


Checks if this node starts a variation (and can thus have a starting comment). The root node does not start a variation and can have no starting comment.


Checks if the node is in the main line of the game.


Checks if this node is the first variation from the point of view of its parent. The root node also is in the main variation.


Gets a child node by move or index.


Checks if the given move appears as a variation.


Promotes the given move to the main variation.


Moves the given variation one up in the list of variations.


Moves the given variation one down in the list of variations.


Removes a variation by move.

add_variation(move, comment='', starting_comment='', nags=())

Creates a child node with the given attributes.

add_main_variation(move, comment='')

Creates a child node with the given attributes and promotes it to the main variation.


chess.pgn.read_game(handle, error_handler=<function _raise>)

Reads a game from a file opened in text mode.

By using text mode the parser does not need to handle encodings. It is the callers responsibility to open the file with the correct encoding. According to the specification PGN files should be ASCII. Also UTF-8 is common. So this is usually not a problem.

>>> pgn = open("data/pgn/kasparov-deep-blue-1997.pgn")
>>> first_game = chess.pgn.read_game(pgn)
>>> second_game = chess.pgn.read_game(pgn)
>>> first_game.headers["Event"]
'IBM Man-Machine, New York USA'

Use StringIO to parse games from a string.

>>> pgn_string = "1. e4 e5 2. Nf3 *"
>>> try:
>>>     from StringIO import StringIO # Python 2
>>> except ImportError:
>>>     from io import StringIO # Python 3
>>> pgn = StringIO(pgn_string)
>>> game = chess.pgn.read_game(pgn)

The end of a game is determined by a completely blank line or the end of the file. (Of course blank lines in comments are possible.)

According to the standard at least the usual 7 header tags are required for a valid game. This parser also handles games without any headers just fine.

The parser is relatively forgiving when it comes to errors. It skips over tokens it can not parse. However it is difficult to handle illegal or ambiguous moves. If such a move is encountered the default behaviour is to stop right in the middle of the game and raise ValueError. If you pass None for error_handler all errors are silently ignored, instead. If you pass a function this function will be called with the error as an argument.

Returns the parsed game or None if the EOF is reached.


Scan a PGN file opened in text mode for game offsets and headers.

Yields a tuple for each game. The first element is the offset. The second element is an ordered dictionary of game headers.

Since actually parsing many games from a big file is relatively expensive, this is a better way to look only for specific games and seek and parse them later.

This example scans for the first game with Kasparov as the white player.

>>> pgn = open("mega.pgn")
>>> for offset, headers in chess.pgn.scan_headers(pgn):
...     if "Kasparov" in headers["White"]:
...         kasparov_offset = offset
...         break

Then it can later be seeked an parsed.

>>> game = chess.pgn.read_game(pgn)

This also works nicely with generators, scanning lazily only when the next offset is required.

>>> white_win_offsets = (offset for offset, headers in chess.pgn.scan_headers(pgn)
...                             if headers["Result"] == "1-0")
>>> first_white_win = next(white_win_offsets)
>>> second_white_win = next(white_win_offsets)
Warning:Be careful when seeking a game in the file while more offsets are being generated.

Scan a PGN file opened in text mode for game offsets.

Yields the starting offsets of all the games, so that they can be seeked later. This is just like scan_headers() but more efficient if you do not actually need the header information.

The PGN standard requires each game to start with an Event-tag. So does this scanner.


If you want to export your game game with all headers, comments and variations you can use:

>>> print(game)
[Event "?"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "?"]
[Black "?"]
[Result "*"]

1. e4 e5 { Comment } *

Remember that games in files should be separated with extra blank lines.

>>> print(game, file=handle, end="\n\n")

Use exporter objects if you need more control. Exporter objects are used to allow extensible formatting of PGN like data.

class chess.pgn.StringExporter(columns=80)

Allows exporting a game as a string.

chess.pgn.Game.export() also provides options to include or exclude headers, variations or comments. By default everything is included.

>>> exporter = chess.pgn.StringExporter()
>>> game.export(exporter, headers=True, variations=True, comments=True)
>>> pgn_string = str(exporter)

Only columns characters are written per line. If columns is None then the entire movetext will be on a single line. This does not affect header tags and comments.

There will be no newlines at the end of the string.

class chess.pgn.FileExporter(handle, columns=80)

Like a StringExporter, but games are written directly to a text file.

There will always be a blank line after each game. Handling encodings is up to the caller.

>>> new_pgn = open("new.pgn", "w")
>>> exporter = chess.pgn.FileExporter(new_pgn)
>>> game.export(exporter)


Numeric anotation glyphs describe moves and positions using standardized codes that are understood by many chess programs. During PGN parsing, annotations like !, ?, !!, etc. are also converted to NAGs.

chess.pgn.NAG_GOOD_MOVE = 1

A good move. Can also be indicated by ! in PGN notation.

chess.pgn.NAG_MISTAKE = 2

A mistake. Can also be indicated by ? in PGN notation.

chess.pgn.NAG_BRILLIANT_MOVE = 3

A brilliant move. Can also be indicated by !! in PGN notation.

chess.pgn.NAG_BLUNDER = 4

A blunder. Can also be indicated by ?? in PGN notation.


A speculative move. Can also be indicated by !? in PGN notation.

chess.pgn.NAG_DUBIOUS_MOVE = 6

A dubious move. Can also be indicated by ?! in PGN notation.