[Jugurtha]

If he's read a few books and knows generators, etc, then I suggest:

"Python Cookbook", which shows you how to do many things (files, networks, servers, binary, data handling). It effectively is a cookbook and helps you have or be aware of several "recipes" to do common things.

To write better Python: Brett Slatkin's "Effective Python: [59|90] Specific Ways to Write Better Python" will get him to write good quality Python code "in general". This could reassure potential employers to some degree.

Having some familiarity or experience with the domain of the organization helps. Python is Python, but there are several subtleties in working writing code that encodes to/decodes from binary packets, or with systems work, or audio processing, etc.

It will depend on whether these companies want someone who "can code", or someone who "can code in Python", or "someone who can code X in Python because that's we're doing X in Python".