With some helpful discussions from the folks in the comments and this similar question, I believe I have found a solution (perhaps not the best solution).

In the src/lib_name/__init__.py file, if I include:

import lib_name.lib_name
from . import file1, file2

Then in a Jupyter notebook, I import the lib as follows:

from lib_name.lib_name import func
func()  # Call the function.

This seems to resolve the name space error I mentioned above.

However, what I still don't understand:

• Why do I need to do lib_name.lib_name? Unless I've misunderstood, I thought the src layout allowed you so only need to call lib_name once?
• Similarly, in the notebook, I have to also do the (rather ugly) double import of lib_name. Why is this? Again, I was of the understanding this could be done with just one import with src layout.
• Why, in the __init__.py file, can I not import all the modules in one line? E.g., from . import lib_name, file1, file2

Any insights on these questions, or recommendations on improving the answer, would still be greatly appreciated.