It sounds like you want to know more about the rationale behind the design of the language, rather than internals. "internals" to me means things like how objects are laid out in memory, how reference counting works, and so on.
If you're looking for a deeper understanding of the design decisions, try reading the PEPs: they are the proposals for changes in the language, and often include detailed discussions of the reasons for the changes, rejected alternatives, and so on. Even the rejected PEPs are useful, because they show the thinking that has shaped the language.
For example:
- 3105: Making print a function
- 3110: Catching exceptions in Python 3.x
- 3131: Supporting non-ASCII identifiers
and so on..
If you really want to learn about Python internals, then start by reading about the Python C API, which is used to build Python itself: my talk A Whirlwind Excursion through Python C Extensions is one place to start. Then you can dive into the Python source code itself for anything you need to learn about.
