Google Python class - YouTube videos (not great)
Part 1(1) - Introduction to Python and strings
Part 1(2) - Working with lists, tuples and sorting
Part 1(3) - Working with dictionaries and files
Part 2(1) - Regular expressions
Part 2(2) - Using modules, system commands
Part 2(3) - Exceptions, parsing URLs
Part 2(4) - List comprehensions
Guide for beginners who are non-programmers
Python's wiki page lists several resources for beginners.
Python Tutor visually helps understand how code executes on a computer.
Here is a small collection of cheat sheets you may find useful:
Python Packages
Other
Programming challenges are a long tradition in computer science.
Four exercises are provided as part of the Python class by Google.
Level - Basic/intermediate
Project Euler is a project of mathematical/programming challenges aimed at designing efficient solutions. Project Euler is a good place to challenge your mathematical and programming skills. Most of the problems can be solved within few seconds provided you have an efficient solution.
Level - Advanced | Requires knowledge of mathematics.
Level - Intermediate/Advanced
Level - Advanced | Requires a lot of cleverness