Below are some featured Python Practice web sites suggested by Jose Portilla in http://www.udemy.com web course Complete Python Bootcamp. Also the course contains two main milestone projects and a list of 100 other milestone projects, each with sample solutions.
More Mathematical (and Harder) Practice:
List of Practice Problems:
A SubReddit Devoted to Daily Practice Problems:
A very tricky website with very few hints and touch problems (Not for beginners but still interesting)