Polyglot opening book reading¶

chess.polyglot.open_reader(path)¶

Creates a reader for the file at the given path.

>>> with open_reader("data/polyglot/performance.bin") as reader:
...    for entry in reader.find_all(board):
...        print(entry.move(), entry.weight, entry.learn)
e2e4 1 0
d2d4 1 0
c2c4 1 0

class chess.polyglot.Entry¶

An entry from a polyglot opening book.

key¶: The Zobrist hash of the position.

raw_move¶: The raw binary representation of the move. Use the move() method to extract a move object from this.

weight¶: An integer value that can be used as the weight for this entry.

learn¶: Another integer value that can be used for extra information.

move()¶: Gets the move (as a Move object).

class chess.polyglot.MemoryMappedReader(filename)¶

Maps a polyglot opening book to memory.

close()¶: Closes the reader.

find(board, minimum_weight=1)¶

Finds the main entry for the given position or zobrist hash.

The main entry is the first entry with the highest weight.

By default entries with weight 0 are excluded. This is a common way to delete entries from an opening book without compacting it. Pass minimum_weight 0 to select all entries.

Raises IndexError if no entries are found.

find_all(board, minimum_weight=1)¶: Seeks a specific position and yields corresponding entries.

choice(board, minimum_weight=1, random=<module 'random' from '/home/docs/checkouts/readthedocs.org/user_builds/python-chess/envs/v0.10.1/lib/python3.4/random.py'>)¶

Uniformly selects a random entry for the given position.

Raises IndexError if no entries are found.

weighted_choice(board, random=<module 'random' from '/home/docs/checkouts/readthedocs.org/user_builds/python-chess/envs/v0.10.1/lib/python3.4/random.py'>)¶

Selects a random entry for the given position, distributed by the weights of the entries.

Raises IndexError if no entries are found.

chess.POLYGLOT_RANDOM_ARRAY = [0x9D39247E33776D41, ..., 0xF8D626AAAF278509]¶: Array of 781 polyglot compatible pseudo random values for Zobrist hashing.