Challenges

HackerEarth, HackerRank, LeetCode, bynarysearch, py.checkio, codewars, projecteuler (my solutions + other's solutions for the problems posted on these sites)

https://www.hackerearth.com/practice/

https://www.hackerrank.com/domains/python

https://leetcode.com/problemset/all/

https://binarysearch.com/problems

https://py.checkio.org

https://www.codewars.com/

https://projecteuler.info/