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A realtime debugging and testing plugin for the Python Language Server.

Project description

A realtime debugging and testing plugin for the Python Language Server (pylsp).

Who is it for?

Anyone who creates/maintains projects in Python.


Debugging and testing tends to be fairly separate from editing code. Typically a developer needs to run tests each time changes are made and a file saved, and start a debug session when a non-obvious error is found. This slows down the development process considerably.

This plugin uses features provided by the language server protocol (LSP) - as implemented in pylsp - to run tests and provide debugging data* whenever code is updated, making the debug+test feedback process realtime.

How can I start using it?

  • Install pylsp into an IDE with LSP support (instructions).

  • Install pyls-livepy into pylsp, specifying the “pyls” extra.
    pip install pyls-livepy[pyls]
  • Ensure your project has a pyproject.toml file created with poetry.

  • Install pyls-livepy into the project, specifying the “runs” extra.
    poetry add --dev pyls-livepy[runs]
  • Install nox (with toml) so it can be ran from within the project (globally is recommended).

  • Open a Python project file in the editor to ensure pyls-livepy is detected, and to generate the nox config.

  • Run nox at least once to create the project’s environment.

  • Write doctests and pytest cases** as you write your code; any failing/throwing tests will be marked.

  • To disable per project, create a file called disable-pyls-livepy in the project’s root folder.

What is the (default) expected behavior?

In addition to making debugging and testing easier, this plugin also aims to promote the use of modern methods and tools for working with Python projects. It can be configured for other tools, but no configuration is required when nox, poetry and pytest are used. By default, the plugin:

  • Creates a in the project, or a pyls-livepy session is added if one exists (once a project file is accessed).

  • Uses poetry to install the project into an existing nox environment.

  • Runs tests on every syntatically correct change.

  • Indicates failing/exception-throwing tests via LSP diagnostic markers.

Where can I find more information?

Further documentation is a work in progress.


  • Due to the fact that this plugin must be installed into the project, and it was created for Python v3.7, the project must also use minimum 3.7.

  • * Debug data view functionality has not yet been implemented (as of v0.1.0).

  • ** Individual pytest cases can also be ran by importing run_pytest_case from pyls_livepy and passing a CLI string that selects a test, within the doctest. The test file name MUST be the name of the tested module prepended by “test_”, and the module MUST be imported at the global level.

  • This project has been set up using PyScaffold 3.2.3. For details and usage information on PyScaffold see

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