Links for Python Practice:
Basic Practice:
http://codingbat.com/python

More Mathematical (and Harder) Practice:
https://projecteuler.net/archives

List of Practice Problems:
http://www.codeabbey.com/index/task_list

A SubReddit Devoted to Daily Practice Problems:
https://www.reddit.com/r/dailyprogrammer

A very tricky website with very few hints and tough problems (Not for beginners)
http://www.pythonchallenge.com/