JupyterLab Templates

Initialize a Project

Run the following commands to create a project directory, my-project, cd into it, and copy the flake template from the jupyenv repository.

mkdir my-project
cd my-project
nix flake init --template github:tweag/jupyenv

Your project directory will be populated with a flake.nix file and a kernels directory.

Quick Start

Run the following to start JupyterLab:

nix run

JupyterLab will start up and you can start using it inside your browser. The default kernels generally only have standard libraries and packages available. If you want to extend the kernels to have additional libraries and packages, see the following sections.

Kernels

Extending Kernels

By extending a kernel, we mean modifying the arguments given to an available kernel. Open up the kernels/python.nix kernel and you should see something like the following:

python.nix

{
  name,
  availableKernels,
  extraArgs,
}:
availableKernels.python {
  name = "custom-${name}";  # must be unique
  displayName = "custom ${name}";
}

As a simple starter, let us add numpy to the Python kernel and change the names to be more descriptive.

python.nix

{
  name,
  availableKernels,
  extraArgs,
}:
availableKernels.python {
  name = "python-with-numpy"; # must be unique
  displayName = "python with numpy";
  extraPackages = ps: [ ps.numpy ];
}

We have added the extraPackages attribute, a function which takes a package set, ps, as an argument and returns a list of packages. Anything available as a python package in nixpkgs should be added as easily as we added numpy. For example, if we wanted to add scipy and pandas, we could modify the list to be [ ps.numpy ps.scipy ps.pandas ].

We also modified the name and displayName attributes. Modifying displayName is not necessary but makes it easier to distinguish from other kernels in the JupyterLab Web UI.

Tip

One very important note is that if you have multiple kernel files in your project, they must all have unique name attributes.

Info

The extraPackages argument is used with poetry2nix and it takes a function that returns a list. We are using mkPoetryEnv from poetry2nix which uses python.withPackages -- see the related documentation for details.

Extending Kernels (Advanced)

While you can provide extraPackages as seen previously, you are relying on the version of the package in nixpkgs. If you want to specify particular versions, it is easier to extend the kernel using Poetry. Below is a tree structure showing where our new kernel will be created. Our new kernel will be located in custom-python under the kernels directory. We will create the default.nix and pyproject.toml files and the poetry.lock file will be generated for us using poetry.

my-project/
└── kernels/
    └── custom-python/
        ├── default.nix
        ├── pyproject.toml
        └── poetry.lock

1. The first step is to create a directory to put our new kernel which I named custom-python.

2. The easiest way to create the pyproject.toml file is to copy it from the existing kernel in the repository. I have copied the Python kernels pyproject.toml file and added a numpy dependency under tool.poetry.dependencies.

   pyproject.toml

   [tool.poetry]
   name = "jupyter-nix-kernel-ipython"
   version = "0.1.0"
   description = ""
   authors = []
   
   [tool.poetry.dependencies]
   python = "^3.9"
   numpy = "^1.23.0"
   ipykernel = "^6.15.0"
   
   [tool.poetry.dev-dependencies]
   # build systems for dependencies
   hatchling = "^1.3.1"
   
   [build-system]
   requires = ["poetry-core>=1.0.0"]
   build-backend = "poetry.core.masonry.api"
   

3. Generate a poetry.lock file by running poetry lock in the kernel directory, custom-python.

4. Below is the default.nix file which looks similar to the file in the previous example. However now we are overriding the projectDir attribute of the available kernel and setting it to the current directory. This tells poetry2nix to look in the current directory for the pyproject.toml and poetry.lock files which will create a new Python kernel with the version of numpy that we specified. Similar to before we set the name and displayName attribute so we can distinguish it from other kernels.

   default.nix

   {
     name,
     availableKernels,
     extraArgs,
   }:
   availableKernels.python {
     projectDir = ./.;
     displayName = "Python with Numpy 1.23.x";
     name = "my-python-with-numpy";
   }
   

5. From the project top level directory, run nix run. This make take some time as new packages and dependencies have to be fetched. Eventually, you will see the recognizable messages from JupyterLab in your terminal. Open up the Web UI in your browser and use your custom kernel.

Custom Kernels

TODO

Extensions

Stateful Extensions

JupyterLab extensions can be statefully installed using the CLI or Web UI as shown in the JupyterLab Extensions documentation. To use the CLI, the jupyter binary is located in the result directory and can be run as follows: ./result/bin/jupyter labextension install <extension>.

Pure Extensions

TODO