The question isn't shell OR Python.
My shell scripts call Python scripts, many of white I wrote myself. That is working as intended.
I guess this is a huge misconception about shell that I have to write a blog post about.
For Unix-like design patterns in this area, look at Raymond's "The Art of Unix Programming". It discusses the prioritization of command line arguments over environment variables and configuration files, and so on.
I recommend the book The Art of Unix Programming by ESR. It covers choice of editor, programming language, etc. It also gives a good sense for the mindset behind programming on Unix or Linux.
For editors, you probably want either Vim or Emacs. They are both different and which one is better is more about personal taste than anything else. I use Vim. It is great for quickly moving around the code and making changes. I didn't like Emacs as much but many people do. Emacs is extremely extensible and can be used for everything from a news reader to an ide. Try both and see what you like.
If You want deep dive into Linux hacking read already mentioned "Advanced Programming In The UNIX Environment". But IMO this book required some experience before reading it.
I suggest some books about programming tools (used in Linux but not only) like svn, diff, packaging system:
Linux for Programmers and Users - lot of informations for Linux programmers and users
The Linux Programmer's Toolbox - vary good book about Linux tools for programmers.
The Art of UNIX Programming IMO every programmer should read this book, there is a little source code, a a lot of philosophy (some one may don't like it) but most important is it show beautifully of
Unix design, and show how to follow it in your own programs.