My advice would be: have some particular goal in mind, some app that you, or even better someone else, would use in a real world scenario.
I started with the same book Chris B mentioned, i.e. Rapid GUI Programming with Python and Qt and I found it useful and it touched many of the topics you would need in most GUI applications. Additionally, after some time and some confidence gained, you want to have PyQT Classes handy.
Do not avoid C++ examples to explain some problem you'd like to solve, rewriting it in Python is not that hard (depending on the problem, and scope of course).
