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Package for managing conda environment-based kernels inside of Jupyter
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conda-recipe Add retry/timeout loop to tests, tweak windows command Mar 28, 2019
nb_conda_kernels Minor cleanups, test improvements Apr 7, 2019
LICENSE use real notebook 4.2 Apr 19, 2016 use versioneer Aug 20, 2018
appveyor.yml Minor cleanups, test improvements Apr 7, 2019
requirements.txt Minor cleanups, test improvements Apr 7, 2019
setup.cfg Minor cleanups, test improvements Apr 7, 2019 use versioneer Aug 20, 2018

Travis Status AppVeyor status Anaconda-Server Badge
conda install jupycon/label/dev::nb_conda_kernels Anaconda-Server Badge
conda install defaults::nb_conda_kernels Anaconda-Server Badge
conda install conda-forge::nb_conda_kernels Anaconda-Server Badge


This extension enables a Jupyter Notebook or JupyterLab application in one conda environment to access kernels for Python, R, and other languages found in other environments. When a kernel from an external environment is selected, the kernel conda environment is automatically activated before the kernel is launched. This allows you to utilize different versions of Python, R, and other languages from a single Jupyter installation.

The package works by defining a custom KernelSpecManager that scans the current set of conda environments for kernel specifications. It dynamically modifies each KernelSpec so that it can be properly run from the notebook environment. When you create a new notebook, these modified kernels will be made available in the selection list.


This package is designed to be managed solely using conda. It should be installed in the environment from which you run Jupyter Notebook or JupyterLab. This might be your base conda environment, but it need not be. For instance, if the environment notebook_env contains the notebook package, then you would run

conda install -n notebook_env nb_conda_kernels

Any other environments you wish to access in your notebooks must have an appropriate kernel package installed. For instance, to access a Python environment, it must have the ipykernel package; e.g.

conda install -n python_env ipykernel

To utilize an R environment, it must have the r-irkernel package; e.g.

conda install -n r_env r-irkernel

For other languages, their corresponding kernels must be installed.


This extension works only with Jupyter notebooks and JupyterLab. Unfortunately, it does not currently work with Jupyter Console, nbconvert, and other tools. This is because these tools were not designed to allow for the use of custom KernelSpecs.

A new kernel discovery system is being developed for Jupyter 6.0 that should enable the wider Jupyter ecosystem to take advantage of these external kernels. This package will require modification to function properly in this new system.


This package introduces two additional configuration options:

  • env_filter: Regex to filter environment path matching it. Default: None (i.e. no filter)
  • name_format: String name format; '{0}' = Language, '{1}' = Kernel. Default: '{0} [conda env:{1}]'


  1. Install Anaconda or Miniconda.

  2. Create a development environment.

    conda create -n nb_conda_kernels pip python=YOUR_FAVORITE_PYTHON
    # Linux / Mac
    conda activate nb_conda_kernels
    # Windows
    activate nb_conda_kernels
    # Install the package and test dependencies
    conda install --file requirements.txt
  3. Install the source package in development mode.

    pip install -e .
    python -m nb_conda_kernels.install --enable

    Note: there is no longer any need to supply a --prefix argument to the installer.

  4. In order to properly exercise the package, the tests assume a number of requirements:

    • ipykernel in the base/root environment
    • one additional environment with ipykernel
    • one environment with r-irkernel
    • one environment with a space in the name
    • one environment with a non-ASCII character in the name

    An easy way to accomplish this is to use the environment specifications in the conda-recipe directory:

    conda install -n root ipykernel
    conda env create -f conda-recipe/testenv1.yaml
    conda env create -f conda-recipe/testenv2.yaml
  5. To run all of the tests, run the command pytest -m nb_conda_kernels.



  • Adds project name to kernel name for environments that live outside of the default environment location
  • Improved runner scripts: linear execution, better handling of environment variables
  • Migrate from nosetests to pytest


  • Put the default environment back into the conda-env list; the redundancy is worth the elimination of confusion.
  • Fix post-link scripts on windows


  • Perform full activation of kernel conda environments
  • Discover kernels from their kernel specs, enabling the use of kernels besides Python and R
  • Support for spaces and accented characters in environment paths, with properly validating kernel names
  • Configurable format for kernel display names
  • Remove NodeJS-based testing


  • move to a full conda-based approach to build and test
  • add support for conda 4.4 and later, which can remove conda from the PATH


  • add support for regex-based filtering of conda environments that should not appear in the list


  • change kernel naming scheme to leave default kernels in place


  • ignore build cleanup on windows due to poorly-behaved PhantomJS processes



  • minor build changes


  • update to notebook 4.2
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