Ubuntu – Jupyter Notebook not Starting in Virtual Environment

Environment

• Ubuntu 20.04
• Python 3.8.10
• Pip 20.0.2

Using pip venv to create a virtual environment in my project directory. These are the commands I am running.

python3 -m pip venv .venv # Create the virtual environment
source .venv/bin/activate 
(.venv) $ time python3 -m pip install --requirement pip_requirements.txt # Inside the venv

My pip_requirements.txt has the following dependencies listed (among others)

jupyterlab
jupyter
notebook
ipython
ipykernel

So when I try to run jupyter notebook inside the venv, this is the error I get.

(.venv) della@workstation:~/Python_scripts/email-classification$  jupyter-notebook
(.venv) della@workstation:~/Python_scripts/email-classification$  jupyter notebook
Traceback (most recent call last):
  File "/home/della/.local/bin/jupyter-notebook", line 5, in <module>
    from notebook.app import main
  File "/home/della/.local/lib/python3.8/site-packages/notebook/app.py", line 20, in <module>
    from jupyterlab.commands import (  # type:ignore[import-untyped]
ModuleNotFoundError: No module named 'jupyterlab'

Tried with both space and hyphen in jupyter notebook and I get the same result.

When I look at the path, I see two things happening the interpreter is going outside the venv to look for the executable script. Should it happen at all when venv is meant to provide isolation? How can I run jupyter inside the venv with packages available only in the venv?

More information. When I try to see the executable for jupyter, I get one inside the venv.

(.venv) della@workstation:~/Python_scripts/email-classification$ which jupyter notebook -a
/home/della/Python_scripts/email-classification/.venv/bin/jupyter