Troubleshooting
===============

NoSuchKernel Errors (using Conda)
---------------------------------

``NoSuchKernel`` Errors can appear when running papermill on jupyter notebooks whose
kernel has been specified via conda (nb_conda). nb_conda is used to easily set
conda environment per notebook from within jupyterlab.

To illustrate, the following example demonstrates the creation of a new
environment with all the dependencies necessary for an analysis.

::

  conda create -n analysis_1 python=2 ipykernel

Once nb_conda is used within the jupyter server to set the kernel for a
notebook to *analysis_1*, the notebook gets metadata similar to the following:

.. code-block:: json

  {
   "kernelspec": {
    "display_name": "Python [conda env:analysis_1]",
    "language": "python",
    "name": "conda-env-analysis_1-py"
   }
  }

Papermill cannot use this metadata to determine that it should use
*analysis_1* to execute this notebook. Running papermill (from *analysis_1* or
another environment) will raise the following error:

::

  jupyter_client.kernelspec.NoSuchKernel: No such kernel named conda-env-analysis_1-py

This can be fixed by:

* Installing jupyter
  (`or at least ipykernel <https://ipython.readthedocs.io/en/stable/install/kernel_install.html#kernels-for-different-environments>`_)
  in *analysis_1*

::

  conda install -n analysis_1 jupyter

* Expose the *analysis_1* environment as a jupyter kernel
  (`this is no longer automatic <https://github.com/jupyter/jupyter/issues/245>`_).

::

  conda activate analysis_1
  jupyter kernelspec install --user --name analysis_1

* Run papermill (from any environment) specifying the correct kernel using the
  ``-k`` option

::

  papermill my_notebook.ipynb output_notebook.ipynb -k analysis_1