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A Fable (python) kernel for Jupyter

Project description

F# and Fable (Python) support for Jupyter

Fable Python is an F# kernel for Jupyter based on Fable and IPythonKernel. Fable is a transpiler that converts F# to Python (and JavaScript).

This work is work-in-progress and related to


Make sure you have a recent version of .NET installed on your machine:

You also need to install the fable-py .NET tool globally (and make sure it's available in PATH environment)

dotnet tool install -g fable-py --version 4.0.0-alpha-026

pip install fable-py
python -m fable_py install

To use the very latest changes (for development):

git clone
cd Fable.Jupyter
python develop
python -m fable_py install


You can use Fable Python in the Jupyter notebook by selecting the "F# (Fable Python)" kernel. To start Jupyter run e.g:

jupyter notebook

# or

jupyter lab

Magic commands

You can inspect the generated Python code by executing %python in a cell:


You can inspect the maintained F# program by executing %fsharp in a cell:


F# Program

The kernel works by maintaining an F# program Fable.fs behind the scenes. This program lives in a separate tmp folder for each instance of the kernel.

Sometimes the generated F# program might become invalid because of the submitted code fragments (this can happen with a Python notebook as well). The way to recover is to reset the kernel. That will reset the F# program that is running behind the notebook. To reset the kernel select on the menu: Kernel -> Restart or Kernel -> Restart & Clear Output.

or you can use the reset command:


If you need additional package references you currently need to add them manually to the Fable.fsproj project file. TODO: handle #r nuget "... commands from within the notebook.

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