Stockfish

Note

This section refers to the technical application. If you are looking for information regarding the status of this project and the original repo, please look here.

Implements an easy-to-use Stockfish class to integrates the Stockfish chess engine with Python.

Install

$ pip install stockfish

Ubuntu

$ sudo apt install stockfish

Mac OS

$ brew install stockfish

API Documentation

See API Documentation for more information.

Technical details and setup

• The codebase is compatible with Python3.7+
• Run pip install -r requirements.txt to get all necessary dependencies.
• Pytest is used to run the unit tests in /tests
• For linting use pre-commit by running pre-commit install once and the pre-commit hooks will be executed automatically

Features and usage examples

Initialize Stockfish class

You should install the stockfish engine in your operating system globally or specify path to binary file in class constructor

from stockfish import Stockfish

stockfish = Stockfish(path="/Users/zhelyabuzhsky/Work/stockfish/stockfish-9-64")

There are some default engine settings used by this wrapper. For increasing Stockfish's strength and speed, the "Threads" and "Hash" parameters can be modified.

{
    "Debug Log File": "",
    "Contempt": 0,
    "Min Split Depth": 0,
    "Threads": 1, # More threads will make the engine stronger, but should be kept at less than the number of logical processors on your computer.
    "Ponder": False,
    "Hash": 16, # Default size is 16 MB. It's recommended that you increase this value, but keep it as some power of 2. E.g., if you're fine using 2 GB of RAM, set Hash to 2048 (11th power of 2).
    "MultiPV": 1,
    "Skill Level": 20,
    "Move Overhead": 10,
    "Minimum Thinking Time": 20,
    "Slow Mover": 100,
    "UCI_Chess960": False,
    "UCI_LimitStrength": False,
    "UCI_Elo": 1350
}

You can change them, as well as the default search depth, during your Stockfish class initialization:

stockfish = Stockfish(path="/Users/zhelyabuzhsky/Work/stockfish/stockfish-9-64", depth=18, parameters={"Threads": 2, "Minimum Thinking Time": 30})

These parameters can also be updated at any time by calling the "update_engine_parameters" function:

stockfish.update_engine_parameters({"Hash": 2048, "UCI_Chess960": True}) # Gets stockfish to use a 2GB hash table, and also to play Chess960.

When you're done using the Stockfish engine process, you can send the "quit" uci command to it with:

stockfish.send_quit_command()

The __del__() method of the Stockfish class will call send_quit_command(), but it's technically not guaranteed python will call __del__() when the Stockfish object goes out of scope. So even though it'll probably not be needed, it doesn't hurt to call send_quit_command() yourself.

Set position by a sequence of moves from the starting position

stockfish.set_position(["e2e4", "e7e6"])

Update position by making a sequence of moves from the current position

stockfish.make_moves_from_current_position(["g4d7", "a8b8", "f1d1"])

Set position by Forsyth–Edwards Notation (FEN)

If you'd like to first check if your fen is valid, call the is_fen_valid() function below. Also, if you want to play Chess960, it's recommended you first update the "UCI_Chess960" engine parameter to be True, before calling set_fen_position.

stockfish.set_fen_position("rnbqkbnr/pppp1ppp/4p3/8/4P3/8/PPPP1PPP/RNBQKBNR w KQkq - 0 2")

Check whether the given FEN is valid

This function returns a bool saying whether the passed in FEN is valid (both syntax wise and whether the position represented is legal). The function isn't perfect and won't catch all cases, but generally it should return the correct answer. For example, one exception is positions which are legal, but have no legal moves. I.e., for checkmates and stalemates, this function will incorrectly say the fen is invalid.

stockfish.is_fen_valid("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1")

True

stockfish.is_fen_valid("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq -") # will return False, in this case because the FEN is missing two of the six required fields.

False

Get best move

stockfish.get_best_move()

d2d4

It's possible to specify remaining time on black and/or white clock. Time is in milliseconds.

stockfish.get_best_move(wtime=1000, btime=1000)

Get best move based on a time constraint

stockfish.get_best_move_time(1000)

Time constraint is in milliseconds

e2e4

Check if a move is legal in the current position

stockfish.is_move_correct('a2a3')

True

Get info on the top n moves

Get moves, centipawns, and mates for the top n moves. If the move is a mate, the Centipawn value will be None, and vice versa. Note that if you have stockfish on a weaker elo or skill level setting, the top moves returned by this function will still be for full strength.

stockfish.get_top_moves(3)
# [
#   {'Move': 'f5h7', 'Centipawn': None, 'Mate': 1},
#   {'Move': 'f5d7', 'Centipawn': 713, 'Mate': None},
#   {'Move': 'f5h5', 'Centipawn': -31, 'Mate': None}
# ]

Optional parameter verbose (default False) specifies whether to include the full info from the engine in the returned dictionary, including SelectiveDepth, Nodes, NodesPerSecond, Time, MultiPVLine, and WDL if available.

stockfish.get_top_moves(1, verbose=True)
# [{
#   "Move":"d6e7",
#   "Centipawn":-408,
#   "Mate":"None",
#   "Nodes":"2767506",
#   "NodesPerSecond":"526442",
#   "Time":"5257",
#   "SelectiveDepth":"31",
#   "MultiPVLine":"1",
#   "WDL":"0 0 1000"
# }]

Optional parameter num_nodes specifies the number of nodes to search. If num_nodes is 0, then the engine will search until the configured depth is reached.

Get perft information

The perft command is used to test the move generation. It counts the total number of leaf nodes to a certain depth, and shows how this node count is divided amongst all legal moves of the current position.

The depth parameter should be an integer greater than zero and specifies the search depth.

stockfish.get_perft(3)
# (8902, {'a2a3': 380, 'b2b3': 420, 'c2c3': 420, 'd2d3': 539,
#         'e2e3': 599, 'f2f3': 380, 'g2g3': 420, 'h2h3': 380,
#         'a2a4': 420, 'b2b4': 421, 'c2c4': 441, 'd2d4': 560,
#         'e2e4': 600, 'f2f4': 401, 'g2g4': 421, 'h2h4': 420,
#         'b1a3': 400, 'b1c3': 440, 'g1f3': 440, 'g1h3': 400})

Flip

Flip the side to move.

stockfish.get_fen_position()
# rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
stockfish.flip()
stockfish.get_fen_position()
# rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR b KQkq - 0 1

Set perspective of the evaluation

You can set the perspective of the evaluation to be from the perspective of the side to move, or from the perspective of White. Currently this setting only applies to get_top_moves().

# Set the perspective of the evaluation to be from the point of view of the side to move
stockfish.set_turn_perspective(True)

# Set the perspective of the evaluation to be from White's perspective
stockfish.set_turn_perspective(False)

# Get the current perspective of the evaluation
is_turn_perspective = stockfish.get_turn_perspective()

Get Stockfish's win/draw/loss stats for the side to move in the current position

Before calling this function, it is recommended that you first check if your version of Stockfish is recent enough to display WDL stats. To do this, use the "does_current_engine_version_have_wdl_option()" function below.

stockfish.get_wdl_stats() # include the argument get_as_tuple=True if you'd like to have a tuple returned instead of a list.

[87, 894, 19]

Find if your version of Stockfish is recent enough to display WDL stats

stockfish.does_current_engine_version_have_wdl_option()

True

Set the engine's skill level (ignoring ELO rating)

stockfish.set_skill_level(15)

Set the engine's ELO rating (ignoring skill level)

stockfish.set_elo_rating(1350)

Put the engine back to full strength (if you've previously lowered the ELO or skill level)

stockfish.resume_full_strength()

Set the engine's depth

stockfish.set_depth(15)

Get the engine's current parameters

stockfish.get_engine_parameters()

{
    "Debug Log File": "",
    "Contempt": 0,
    "Min Split Depth": 0,
    "Threads": 1,
    "Ponder": False,
    "Hash": 16,
    "MultiPV": 1,
    "Skill Level": 20,
    "Move Overhead": 10,
    "Minimum Thinking Time": 20,
    "Slow Mover": 100,
    "UCI_Chess960": False,
    "UCI_LimitStrength": False,
    "UCI_Elo": 1350
}

Reset the engine's parameters to the default

stockfish.reset_engine_parameters()

Get the current board position in Forsyth–Edwards notation (FEN)

stockfish.get_fen_position()

rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1

Get the current board visual

stockfish.get_board_visual()

+---+---+---+---+---+---+---+---+
| r | n | b | q | k | b | n | r | 8
+---+---+---+---+---+---+---+---+
| p | p | p | p | p | p | p | p | 7
+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   | 6
+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   | 5
+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   | 4
+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   | 3
+---+---+---+---+---+---+---+---+
| P | P | P | P | P | P | P | P | 2
+---+---+---+---+---+---+---+---+
| R | N | B | Q | K | B | N | R | 1
+---+---+---+---+---+---+---+---+
  a   b   c   d   e   f   g   h

This function has an optional boolean (True by default) as a parameter that indicates whether the board should be seen from the view of white. So it is possible to get the board from black's point of view like this:

stockfish.get_board_visual(False)

+---+---+---+---+---+---+---+---+
| R | N | B | K | Q | B | N | R | 1
+---+---+---+---+---+---+---+---+
| P | P | P | P | P | P | P | P | 2
+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   | 3
+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   | 4
+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   | 5
+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   | 6
+---+---+---+---+---+---+---+---+
| p | p | p | p | p | p | p | p | 7
+---+---+---+---+---+---+---+---+
| r | n | b | k | q | b | n | r | 8
+---+---+---+---+---+---+---+---+
  h   g   f   e   d   c   b   a

Get the current position's evaluation in centipawns or mate in x

Stockfish searches to the specified depth and evaluates the current position:

stockfish.get_evaluation()

Instead of using the depth, you can also specify the time the engine should take to evaluate:

stockfish.get_evaluation(searchtime=2000) # searchtime in milliseconds

A dictionary is returned representing the evaluation. Two example return values:

{"type":"cp", "value":12}

{"type":"mate", "value":-3}

If stockfish.get_turn_perspective() is True, then the eval value is relative to the side to move. Otherwise, positive is advantage white, negative is advantage black.

Get the current position's 'static evaluation'

stockfish.get_static_eval()

Sends the 'eval' command to Stockfish. This will get it to 'directly' evaluate the current position (i.e., no search is involved), and output a float value (not a whole number centipawn).

If one side is in check or mated, recent versions of Stockfish will output 'none' for the static eval. In this case, the function will return None.

Some example return values:

-5.27

0.28

None

Run benchmark

BenchmarkParameters

params = BenchmarkParameters(**kwargs)

parameters required to run the benchmark function. kwargs can be used to set custom values.

ttSize: range(1,128001)
threads: range(1,513)
limit: range(1,10001)
fenFile: "path/to/file.fen"
limitType: "depth", "perft", "nodes", "movetime"
evalType: "mixed", "classical", "NNUE"

stockfish.benchmark(params)

This will run the bench command with BenchmarkParameters. It is an additional custom non-UCI command, mainly for debugging. Do not use this command during a search!

Get the major version of the stockfish engine being used

E.g., if the engine being used is Stockfish 14.1 or Stockfish 14, then the function would return 14. Meanwhile, if a development build of the engine is being used (not an official release), then the function returns an int with 5 or 6 digits, representing the date the engine was compiled on. For example, 20122 is returned for the development build compiled on January 2, 2022.

stockfish.get_stockfish_major_version()

15

Find if the version of Stockfish being used is a development build

stockfish.is_development_build_of_engine()

False

Find what is on a certain square

If the square is empty, the None object is returned. Otherwise, one of 12 enum members of a custom Stockfish.Piece enum will be returned. Each of the 12 members of this enum is named in the following pattern: colour followed by underscore followed by piece name, where the colour and piece name are in all caps. For example, say the current position is the starting position:

stockfish.get_what_is_on_square("e1") # returns Stockfish.Piece.WHITE_KING
stockfish.get_what_is_on_square("d8") # returns Stockfish.Piece.BLACK_QUEEN
stockfish.get_what_is_on_square("h2") # returns Stockfish.Piece.WHITE_PAWN
stockfish.get_what_is_on_square("b5") # returns None

Find if a move will be a capture (and if so, what type of capture)

The argument must be a string that represents the move, using the notation that Stockfish uses (i.e., the coordinate of the starting square followed by the coordinate of the ending square). The function will return one of the following enum members from a custom Stockfish.Capture enum: DIRECT_CAPTURE, EN_PASSANT, or NO_CAPTURE. For example, say the current position is the one after 1.e4 Nf6 2.Nc3 e6 3.e5 d5.

stockfish.will_move_be_a_capture("c3d5")  # returns Stockfish.Capture.DIRECT_CAPTURE
stockfish.will_move_be_a_capture("e5f6")  # returns Stockfish.Capture.DIRECT_CAPTURE
stockfish.will_move_be_a_capture("e5d6")  # returns Stockfish.Capture.EN_PASSANT
stockfish.will_move_be_a_capture("f1e2")  # returns Stockfish.Capture.NO_CAPTURE

StockfishException

The StockfishException is a newly defined Exception type. It is thrown when the underlying Stockfish process created by the wrapper crashes. This can happen when an incorrect input like an invalid FEN (for example 8/8/8/3k4/3K4/8/8/8 w - - 0 1 with both kings next to each other) is given to Stockfish.
Not all invalid inputs will lead to a StockfishException, but only those which cause the Stockfish process to crash.
To handle a StockfishException when using this library, import the StockfishException from the library and use a try/except-block:

from stockfish import StockfishException

try:
    # Evaluation routine

except StockfishException:
    # Error handling

Debug view

You can (de-)activate the debug view option with the set_debug_view function. Like this you can see all communication between the engine and the library.

stockfish.set_debug_view(True)

Contributing

Most contributions will involve making updates to stockfish/models.py. To test your changes, download a version of stockfish and paste the executable in the stockfish folder. Then, create a file in the stockfish folder called main.py. Both the executable and main.py will be ignored by git. In main.py, start with something like the following:

from models import Stockfish

def main():
    sf = Stockfish(path = "name of your stockfish executable")
    # Use this object as you wish to test your changes.

if __name__ == "__main__":
    main()

Then when navigating to the stockfish folder in the terminal, you can run this main.py file simply with python main.py. Once you're satisfied with your changes to models.py, see the section below for how to run the project's entire test suite.

Testing

For your stockfish executable (the same one mentioned in the previous section), paste it also in the project's root directory. Then in models.py, temporarily modify this line so that the path's default value is changed from "stockfish" to the name of your stockfish executable:

path: str = "stockfish",

Then in the project's root directory, you can run:

$ python setup.py test

To skip some of the slower tests, run:

$ python setup.py skip_slow_tests

Security

If you discover any security related issues, please report it via the Private vulnerability reporting instead of using the issue tracker.

Status of the project

Note This is just a brief summary. For more information, please look here.

Due to the unfortunate death of Ilya Zhelyabuzhsky, the original repo is no longer maintained. For this reason, this fork was created, which continues the project and is currently maintained by johndoknjas and kieferro. The official PyPi releases for the Stockfish package will also be created from this repo in the future.

Please submit all bug reports and PRs to this repo instead of the old one.

Credits

• We want to sincerely thank Ilya Zhelyabuzhsky, the original founder of this project for writing and maintaining the code and for his contributions to the open source community.
• We also want to thank all the other contributors for working on this project.

License

MIT License. Please see License File for more information.