Configuration#

Pre-installed packages#

xeus-python allows you to pre-install packages in the Python runtime. You can pre-install packages by adding an environment.yml file in the JupyterLite build directory, this file will be found automatically by xeus-python which will pre-build the environment when running jupyter lite build.

Furthermore, this automatically installs any labextension that it founds, for example installing ipyleaflet will make ipyleaflet work without the need to manually install the jupyter-leaflet labextension.

Say you want to install NumPy, Matplotlib and ipycanvas, it can be done by creating the environment.yml file with the following content:

name: xeus-python-kernel
channels:
  - https://repo.mamba.pm/emscripten-forge
  - conda-forge
dependencies:
  - numpy
  - matplotlib
  - ipycanvas

Then you only need to build JupyterLite:

jupyter lite build

You can also pick another name for that environment file (e.g. custom.yml), by doing so, you will need to specify that name to xeus-python:

jupyter lite build --XeusPythonEnv.environment_file=custom.yml

Warning

It is common to provide pip dependencies in a conda environment file. This is currently partially supported by xeus-python. See “pip packages” section.

Then those packages are usable directly:

Try it!

pip packages#

⚠ This feature is experimental. You won’t have the same user-experience as when using conda/mamba in a “normal” setup ⚠

xeus-python provides a way to install packages with pip.

There are a couple of limitations that you should be aware of:

  • it can only install pure Python packages (Python code + data files)

  • it does not install the package dependencies, you should make sure to install them yourself using conda-forge/emscripten-forge.

  • it does not work (yet?) using -r requirements.txt in your environment file

For example, if you were to install ipycanvas from PyPI, you would need to install the ipycanvas dependencies for it to work (pillow, numpy and ipywidgets):

name: xeus-python-kernel
channels:
  - https://repo.mamba.pm/emscripten-forge
  - conda-forge
dependencies:
  - numpy
  - pillow
  - ipywidgets
  - pip:
      - ipycanvas

You can also install a local Python package, this is very practical if you want to embed a jupyterlite deployment in your Package documentation, allowing to test the very latest dev version:

name: xeus-python-kernel
channels:
  - https://repo.mamba.pm/emscripten-forge
  - conda-forge
dependencies:
  - pip:
      - ..

Advanced Configuration#

Warning

This section is mostly for reference and should not be needed for regular use of the jupyterlite-xeus-python kernel.

Provide a custom empack_config.yaml#

Packages sometimes ship more data than needed for the package to work (tests, documentation, data files etc). This is fine on a regular installation of the package, but in the emscripten case when running in the browser this means that starting the kernel would download more files. For this reason, empack filters out anything that is not required for the Python code to run. It does it by following a set of filtering rules available in this file: emscripten-forge/empack.

But this default filtering could break some packages. In that case you would probably want to either contribute to the default empack config, or provide your own set of filtering rules.

The xeus-python kernel supports passing a custom empack_config.yaml. This file can be used to override the default filter rules set by the underlying empack tool used for packing the environment.

If you would like to provide additional rules for including or excluding files in the packed environment, create a empack_config.yaml with the following content as an example:

packages:
  xarray:
    include_patterns:
      - pattern: '**/*.py'
      - pattern: '**/static/css/*.css'
      - pattern: '**/static/html/*.html'

This example defines a set of custom rules for the xarray package to make sure it includes some static files that should be available from the kernel.

You can use this file when building JupyterLite:

jupyter lite build --XeusPythonEnv.empack_config=empack_config.yaml

Note

Filtering files helps reduce the size of the assets to download and as a consequence reduce network traffic.