Notebook: edit .py files? Add them to pythonpath?

[switham]

Provide ways to save a block of notebook code in a .py file, edit .py files, and load .py files back into notebook code blocks.

Of course you can always import from a .py file... if it's in the directory with the notebook. Maybe I want a way to make some files or notebooks' directories available on the Python path.

Might want a way to reload a modified module. But that's not trivial in Python itself. Maybe just a way to clear the global space of the current notebook and start running things again.

Of course with a notebook plus a file editor, you can cut and paste between them.