Think Python - Allen Downey - Green Tea Press - 2nd Edition, Version 2.2.20

This is a book for learning Python and "How to Think Like a Computer Scientist". It starts from the beginning (what is a program) and goes up to high level analysis of algorithms. It is published under Creative Commons Attribution-NonCommercial 3.0 Unported License, and you can find it with other books of the author in the authors web site http://greenteapress.com/wp/think-python-2e/