Python LSP Server

A Python 3.9+ implementation of the Language Server Protocol.

Installation

The base language server requires Jedi to provide Completions, Definitions, Hover, References, Signature Help, and Symbols:

pip install python-lsp-server

This will expose the command pylsp on your PATH. Confirm that installation succeeded by running pylsp --help.

If the respective dependencies are found, the following optional providers will be enabled:

• Rope for Completions and renaming
• Pyflakes linter to detect various errors
• McCabe linter for complexity checking
• pycodestyle linter for style checking
• pydocstyle linter for docstring style checking (disabled by default)
• autopep8 for code formatting
• YAPF for code formatting (preferred over autopep8)
• flake8 for error checking (disabled by default)
• pylint for code linting (disabled by default)

Optional providers can be installed using the extras syntax. To install YAPF formatting for example:

pip install "python-lsp-server[yapf]"

All optional providers can be installed using:

pip install "python-lsp-server[all]"

If you get an error similar to 'install_requires' must be a string or list of strings then please upgrade setuptools before trying again.

pip install -U setuptools

Windows and Linux installation

If you use Anaconda/Miniconda, you can install python-lsp-server using this conda command

conda install -c conda-forge python-lsp-server

Python-lsp-server is available in the repos of every major Linux distribution, and it is usually called python-lsp-server or python3-pylsp.

For example, here is how to install it in Debian and Debian-based distributions (E.g. Ubuntu, Pop!_OS, Linux Mint)

sudo apt-get install python3-pylsp

or Fedora Linux

sudo dnf install python3-lsp-server

or Arch Linux

sudo pacman -S python-lsp-server

Only on Alpine Linux the package is named differently. You can install it there by typing this command in your terminal:

apk add py3-lsp-server

3rd Party Plugins

Installing these plugins will add extra functionality to the language server:

• pylsp-mypy: MyPy type checking for Python >=3.8.
• python-lsp-isort: code formatting using isort (automatic import sorting).
• python-lsp-black: code formatting using Black.
• pyls-memestra: detecting the use of deprecated APIs.
• pylsp-rope: Extended refactoring capabilities using Rope.
• python-lsp-ruff: Extensive and fast linting using ruff.

Please see the above repositories for examples on how to write plugins for the Python LSP Server.

cookiecutter-pylsp-plugin is a cookiecutter template for setting up a basic plugin project for python-lsp-server. It documents all the essentials you need to know to kick start your own plugin project.

Please file an issue if you require assistance writing a plugin.

Configuration

Like all language servers, configuration can be passed from the client that talks to this server (i.e. your editor/IDE or other tool that has the same purpose). The details of how this is done depend on the editor or plugin that you are using to communicate with python-lsp-server. The configuration options available at that level are documented in CONFIGURATION.md.

python-lsp-server depends on other tools, like flake8 and pycodestyle. These tools can be configured via settings passed from the client (as above), or alternatively from other configuration sources. The following sources are available:

• pycodestyle: discovered in ~/.config/pycodestyle, setup.cfg, tox.ini and pycodestyle.cfg.
• flake8: discovered in .flake8, setup.cfg and tox.ini

The default configuration sources are pycodestyle and pyflakes. If you would like to use flake8, you will need to:

1. Disable pycodestyle, mccabe, and pyflakes, by setting their corresponding enabled configurations, e.g. pylsp.plugins.pycodestyle.enabled, to false. This will prevent duplicate linting messages as flake8 includes these tools.
2. Set pylsp.plugins.flake8.enabled to true.
3. Change the pylsp.configurationSources setting (in the value passed in from your client) to ['flake8'] in order to use the flake8 configuration instead.

The configuration options available in these config files (setup.cfg etc) are documented in the relevant tools:

• flake8 configuration
• pycodestyle configuration

Overall configuration is computed first from user configuration (in home directory), overridden by configuration passed in by the language client, and then overridden by configuration discovered in the workspace.

As an example, to change the list of errors that pycodestyle will ignore, assuming you are using the pycodestyle configuration source (the default), you can:

1. Add the following to your ~/.config/pycodestyle:

   [pycodestyle]
   ignore = E226,E302,E41
   

2. Set the pylsp.plugins.pycodestyle.ignore config value from your editor

3. Same as 1, but add to setup.cfg file in the root of the project.

Python LSP Server can communicate over WebSockets when configured as follows:

pylsp --ws --port [port]

The following libraries are required for Web Sockets support:

• websockets for Python LSP Server Web sockets using websockets library. refer Websockets installation for more details

You can install this dependency with command below:

pip install 'python-lsp-server[websockets]'

LSP Server Features

• Auto Completion
• Autoimport
• Code Linting
• Code actions
• Signature Help
• Go to definition
• Hover
• Find References
• Document Symbols
• Document Formatting
• Code folding
• Multiple workspaces

Development

Dev install

# (optional) create conda env
conda create --name python-lsp-server python=3.11 -y
conda activate python-lsp-server

pip install -e ".[all,websockets,test]"

Run server with ws

pylsp --ws -v  # Info level logging
pylsp --ws -vv # Debug level logging

To run the test suite:

# requires: pip install ".[test]" (see above)
pytest

Running ruff as a linter and code formatter on the repo:

ruff check .  # linter
ruff check --fix .  # fix all auto-fixable lint issues
ruff format .  # format the document

After adding configuration options to schema.json, refresh the CONFIGURATION.md file with

python scripts/jsonschema2md.py pylsp/config/schema.json CONFIGURATION.md

License

This project is made available under the MIT License.