I recommend you focus on learning 2.x but be aware of how 3.x might/can be different when the tutorial text points it out.
basically, 2.x is already widely proliferated, and the hard rub already came and went in the transition from 2.4 to 2.6. so the basis is very strong and stable; so much so that it's pre-deployed pretty much everywhere. Also, great tools like Blender3D use it as its scripting language (even though there is work on upgrading/integrating 3.x). so with 2.x, you'll be functional out the gate. with 3.x you might have migration/transition issues to contend with until 3.x becomes the defacto standard deployment package.
also, the final nail in the coffin is that the 3.x distribution contains scripts that will automatically upgrade your codes from 2.x to 3.x. i.e. let the python development team worry about transition for you so you can focus on the core functionality of your particular application.
don't really need books to learn python since it's pretty much self-documented (and self-documenting.) just find the doc/html directory in your distribution, and there's all kinds of good stuff there hanging off the index.html. there's tutorial to get you kick started, there's a library reference to get you make you aware of all the different packages that expand the core capabilities. there's a language reference that's not terribly useful for novice programmers, but provides a lot of insight into the design considerations that went into the language construction itself (e.g. original classes v old classes v new classes -- think of it as the history lesson that explains why things look they way they do.) and most 3rd party python packages contain documentation directories that build fairly high quality documentation sets. sure, you'll have to download and install sphinx, jinja2 and some other documentation support packages, but the build sequence is documented and largely automatic. (e.g. once you figure out that matplotlib and basemap packages are the two you need to do basic geospatial mapping, it's suprising how fast you can become functional starting from nothing.)
in the end, google is your friend. search for "pythong
" and usually the set of packages best suited to help you comes up. oh, you might also want to save yourself a lot of headache and just make sure you have the PyDev plugin for Eclipse (or some other IDE capable of assisting you with python specific development.) once you get past the quick-n-dirty tutorial examples and start refactoring your codes into packages and modules, you're gonna want that level of support soonest.
enjoy!