The Pragmatic Programmer https://www.amazon.com/Pragmatic-Programmer-Journeyman-Maste...

Ousterhout's _A Philosophy of Software Design_ (mentioned elsethread) would be mine.

the python cookbook is good. and fluent python is more from principles rather than application (obvs both python specific). I also like philosophy of software design. tiny little book that uses simple example (class that makes a text editor) to talk about complexity, not actually about making a text editor at all.