An implementation of the Language Server Protocol for Python
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mnazbro and gatesn Fix dev setup (#389)
The dev setup was incorrect since it did not describe how to properly use `yarn install`.
Latest commit b0b6eeb Jul 5, 2018


Python Language Server

A Python 2.7 and 3.4+ implementation of the Language Server Protocol.


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

pip install python-language-server

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
  • autopep8 for code formatting
  • YAPF for code formatting (preferred over autopep8)

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

pip install 'python-language-server[yapf]'

All optional providers can be installed using:

pip install 'python-language-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

3rd Party Plugins

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

Please see the above repositories for examples on how to write plugins for the Python Language Server. Please file an issue if you require assistance writing a plugin.


Configuration is loaded from zero or more configuration sources. Currently implemented are:

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

The default configuration source is pycodestyle. Change the pyls.configurationSources setting to ['flake8'] in order to respect flake8 configuration instead.

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

Language Server Features

Auto Completion:

Code Linting with pycodestyle and pyflakes:

Signature Help:

Go to definition:


Find References:

Document Symbols:

Document Formatting:


To run the test suite:

pip install .[test] && tox

Develop against VS Code

The Python language server can be developed against a local instance of Visual Studio Code.

  1. Install VSCode for Mac
  2. From within VSCode View -> Command Palette, then type shell and run install 'code' command in PATH
# Setup a virtual env
virtualenv env
. env/bin/activate

# Install pyls
pip install .

# Install the vscode-client extension
cd vscode-client
yarn install

# Run VSCode which is configured to use pyls
# See the bottom of vscode-client/src/extension.ts for info
yarn run vscode -- $PWD/../

Then to debug, click View -> Output and in the dropdown will be pyls. To refresh VSCode, press Cmd + r


This project is made available under the MIT License.