How to detect whether in Jupyter Notebook or Lab

Question

I am trying to automatically detect whether my library is being run in classic Jupyter Notebook or JupyterLab. I know get_ipython() can tell me whether I'm in a kernel at all, but it doesn't tell me which frontend I'm in.

Answer 1

Perhaps you can check via whether os.getenv('JUPYTERHUB_API_TOKEN') is None or not.

Answer 2

Using psutil module....

import psutil

parent_process = psutil.Process().parent().cmdline()[-1]

if 'jupyter-lab' in parent_process:
    print('You are using Jupyterlab')
elif 'jupyter-notebook' in parent_process:
    print('You are using Jupyter Notebook')
else:
    print('You are using something else')

Answer 3

Based on @mabraham's answer I came up with the following implementation. It it detects ipykernels launched from Jupyter-lab and Jupyter-hub servers.

def is_jupyterlab_session() -> bool:
    """Check whether we are in a Jupyter-Lab session.
    Notes
    -----
    This is a heuristic based process inspection based on the current Jupyter lab
    (major 3) version. So it could fail in the future.
    It will also report false positive in case a classic notebook frontend is started
    via Jupyter lab.
    """
    import psutil

    # inspect parent process for any signs of being a jupyter lab server

    parent = psutil.Process().parent()
    if parent.name() == "jupyter-lab":
        return True
    keys = (
        "JUPYTERHUB_API_KEY",
        "JPY_API_TOKEN",
        "JUPYTERHUB_API_TOKEN",
    )
    env = parent.environ()
    if any(k in env for k in keys):
        return True

    return False