General Resources for Practising Web Development - Gamified

EDABIT: Learn to code with interactive challenges. It's the fastest, easiest, most addictive way to learn.
Flexbox Froggy: Practise Flexbox by playing this game. A game for learning CSS flexbox.
Grid Garden: Practise CSS Grid by playing this game. Welcome to Grid Garden, where you write CSS code to grow your carrot garden!
CSS Diner: Practise CSS selectors by playing this game. It's a fun game to learn and practice CSS selectors.
HTML exercises: Practice your HTML/XHTML skills with small exercises. The website provides answers and an interactive sandbox as well.
Dev Challenges: Practice HTML / CSS with projects.
Frontend Mentor: Practice with projects to improve your skills.
Dash by General Assembly: Learn to code awesome websites in HTML, CSS, and JavaScript.
CSSBattle: A Code-Golfing platform for CSS. Its like competitive programming in frontend development.

Resources for Practicing Python Development

Coding Bat (Python): Practice problems exploring the basics of Python (Beginner, Intermediate)
Exercism: Hundreds of practice problems in Python and many other languages (Beginner, Intermediate, Advanced)
Edabit: Learn to think like a programmer while solving problems (Beginner, Intermediate, Advanced)
CheckIO (Python): Unlock more difficult puzzles as you prove your programming skills (Beginner, Intermediate, Advanced)
Code Wars: Challenge yourself and your friends with competitive coding (Beginner, Intermediate, Advanced)
Leet Code: Practice with thousands of problems and enter programming contests (Beginner, Intermediate, Advanced)
HackerRank: Solve challenges to advance your rank (Beginner, Intermediate, Advanced)