If you need to learn python from scratch – you can start here: http://docs.python.org/tut/tut.html – good begginers guide
If you need to extend your knowledge – continue here http://diveintopython3.ep.io/ – good intermediate level book
If you need perfect skills – complete this http://www.pythonchallenge.com/ – outstanding and interesting challenge
And the perfect source of knowledge is http://docs.python.org/ – collection of all knowledge