A bridge between Lichess API and bots.

• NOTE: Only Python 3.7 or later is supported!
• Download the repo into lichess-bot directory
• Navigate to the directory in cmd/Terminal: cd lichess-bot
• Install pip: apt install python3-pip
• Install virtualenv: pip install virtualenv
• Setup virtualenv: apt install python3-venv

python3 -m venv venv #if this fails you probably need to add Python3 to your PATH
virtualenv venv -p python3 #if this fails you probably need to add Python3 to your PATH
source ./venv/bin/activate
python3 -m pip install -r requirements.txt

• Copy config.yml.default to config.yml
• Edit the variants: supported_variants and time controls: supported_tc from the config.yml as necessary

• Here is a video on how to install the bot: (https://youtu.be/w-aJFk00POQ). Or you may proceed to the next steps.
• NOTE: Only Python 3.7 or later is supported!
• If you don't have Python, you may download it here: (https://www.python.org/downloads/). When installing it, enable "add Python to PATH", then go to custom installation (this may be not necessary, but on some computers it won't work otherwise) and enable all options (especially "install for all users"), except the last . It's better to install Python in a path without spaces, like "C:\Python".
• To type commands it's better to use PowerShell. Go to Start menu and type "PowerShell" (you may use cmd too, but sometimes it may not work).
• Then you may need to upgrade pip. Execute "python -m pip install --upgrade pip" in PowerShell.
• Download the repo into lichess-bot directory.
• Navigate to the directory in PowerShell: cd [folder's adress] (like "cd C:\chess\lichess-bot").
• Install virtualenv: pip install virtualenv.
• Setup virtualenv:

python -m venv .venv (if this fails you probably need to add Python to your PATH)
./.venv/Scripts/Activate.ps1 (.\.venv\Scripts\activate.bat should work in cmd in administator mode) (This may not work on Windows, and in this case you need to execute "Set-ExecutionPolicy RemoteSigned" first and choose "Y" there [you may need to run Powershell as administrator]. After you executed the script, change execution policy back with "Set-ExecutionPolicy Restricted" and pressing "Y")
pip install -r requirements.txt

• Copy config.yml.default to config.yml
• Edit the variants: supported_variants and time controls: supported_tc from the config.yml as necessary (use # to disable certain ones)

• Create an account for your bot on Lichess.org
• NOTE: If you have previously played games on an existing account, you will not be able to use it as a bot account
• Once your account has been created and you are logged in, create a personal OAuth2 token with the "Play as a bot" selected and add a description
• A token e.g. Xb0ddNrLabc0lGK2 will be displayed. Store this in config.yml as the token field. You can also set the token in the environment variable $LICHESS_BOT_TOKEN.
• NOTE: You won't see this token again on Lichess.

• Place your engine(s) in the engine.dir directory
• In config.yml, enter the binary name as the engine.name field (In Windows you may need to type a name with ".exe", like "lczero.exe")
• Leave the weights field empty or see LeelaChessZero section for Neural Nets

WARNING This is irreversible. Read more about upgrading to bot account.

• run python lichess-bot.py -u

• Press CTRL+C
• It may take some time to quit

• Download the weights for the id you want to play from here: https://lczero.org/play/networks/bestnets/
• Extract the weights from the zip archive and rename it to latest.txt
• For Mac/Linux, build the lczero binary yourself following LeelaChessZero/lc0/README
• Copy both the files into the engine.dir directory
• Change the engine.name and engine.engine_options.weights keys in config.yml to lczero and weights.pb.gz
• You can specify the number of engine.uci_options.threads in the config.yml file as well
• To start: python lichess-bot.py

• For Windows modern CPUs, download the lczero binary from https://github.com/LeelaChessZero/lc0/releases ex: lc0-v0.27.0-windows-cpu-dnnl.zip
• Unzip the file, it comes with lc0.exe , dnnl.dll, and a weights file ex: 703810.pb.gz (amongst other files)
• all three main files need to be copied to the engines directory
• the lc0.exe should be doubleclicked and the windows safesearch warning about it being unsigned should be cleared (be careful and be sure you have the genuine file)
• Change the engine.name key in config.yml to lc0.exe, no need to edit config.yml concerning the weights file as the lc0.exe will use whatever *.pb.gz is in the same folder (have only one *pb.gz in the engines directory)
• To start: python lichess-bot.py

Use https://github.com/vochicong/lc0-nvidia-docker to easily run lc0 and lichess-bot inside a Docker container.

As an alternative to creating an entire chess engine and implementing one of the communiciation protocols (UCI or XBoard), a bot can also be created by writing a single class with a single method. The search() method in this new class takes the current board and the game clock as arguments and should return a move based on whatever criteria the coder desires.

Steps to create a homemade bot:

1. Do all the steps in the How to Install
2. In the config.yml, change the engine protocol to homemade
3. Create a class in some file that extends MinimalEngine (in strategies.py).
   • Look at the strategies.py file to see some examples.
   • If you don't know what to implement, look at the EngineWrapper or UCIEngine class.
     • You don't have to create your own engine, even though it's an "EngineWrapper" class.
       The examples just implement search.
4. In the config.yml, change the name from engine_name to the name of your class

   • In this case, you could change it to:

     name: "RandomMove"

• You can specify a different config file with the --config argument.
• Here's an example systemd service definition:

[Unit]
Description=lichess-bot
After=network-online.target
Wants=network-online.target

[Service]
Environment="PYTHONUNBUFFERED=1"
ExecStart=/usr/bin/python3 /home/thibault/lichess-bot/lichess-bot.py
WorkingDirectory=/home/thibault/lichess-bot/
User=thibault
Group=thibault
Restart=always

[Install]
WantedBy=multi-user.target

Thanks to the Lichess team, especially T. Alexander Lystad and Thibault Duplessis for working with the LeelaChessZero team to get this API up. Thanks to the Niklas Fiekas and his python-chess code which allows engine communication seamlessly.

lichess-bot is licensed under the AGPLv3 (or any later version at your option). Check out LICENSE.txt for the full text.