Document JPY_SESSION_NAME environment variable, which contains current notebook's file path

[simonrouse9461]

Problem

Currently there is no official way of retrieving the notebook's file path dynamically during runtime. Although a package called ipynbname is created for this purpose, it is somehow restrictive and doesn't work under all scenarios (for example, it doesn't work if the jupyterlab is running behind a proxy).

Proposed Solution

VisualStudio Code Jupyter extension implemented a mechanism similar to __file__ in pure python script. The file path of current running notebook is saved to a global variable __vsc_ipynb_file__. It would be really helpful if jupyterlab can support a similar mechanism by saving the file path to __ipynb_file__ or something similar.

Additional context

See microsoft/vscode-jupyter#8531

[krassowski]

If you are using the latest versions of IPython/ipykernel and jupyter-serer, then there is an environment variable called JPY_SESSION_NAME which contains the path to the notebook. You can then assign it to __ipynb_file__ if you like:

import os
__ipynb_file__ = os.environ['JPY_SESSION_NAME']

In general, Jupyter works with a variety of kernels, not only with Python, so injecting a runtime variable is rather hard or even impossible to do for all kernels consistently (for example, this may be invalid variable name in some languages).

[krassowski]

Currently there is no official way of retrieving the notebook's file path dynamically during runtime

As per above, this is incorrect. The problem is that this is not documented in JupyterLab documentation. I think it should be as a hint given how frequent this question is (and this issue is probably a duplicate).

[simonrouse9461]

Thanks for the answer!
I tried this approach, os.environ['JPY_SESSION_NAME'] actually gives /path/to/dir/5d2643a2-3a3a-4186-830b-c1d915ca1aad instead of /path/to/dir/notebook.ipynb. It is possible to have the latter supported?

[krassowski]

I do get /path/to/dir/notebook.ipynb. Did you check that you have all latest versions of dependencies I mentioned?

[simonrouse9461]

Thanks for pointing out, it seems that my dependencies are outdated. Updating them solves the problem.

[JasonWeill]

Previous discussion (thanks @krassowski ) — #8012 (comment)