When comparing Python Challenge vs SoloLearn, the Slant community recommends SoloLearn for most people. In the question“What are the best resources to learn Python?” SoloLearn is ranked 9th while Python Challenge is ranked 14th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Practical approach
The site simply presents a variety of interesting challenges that can be solved with a little bit of programming. (While any language works, the challenges work best with Python.)
Pro Completely free
Pro Offline learning mode for mobile apps
Allows learning while disconnected from the net.
Pro Easy for beginners
Anyone can get started with this.
Pro Share and modify others' projects
Pro Browser-based code playgrounds
No software installation needed, just a modern web browser. On mobile devices though the mobile apps are highly recommended.
Pro Excellent mobile apps available
Pro Gamification
XP, levels, badges, certificates, etc.
Cons
Con Beginners will quickly find themselves overwhelmed
The levels get tricky pretty quickly for beginners. Additional resources will be required to pass all levels.
Con Only the most commonly used languages are covered.
C++, Java, JavaScript, C#, Python, SQL, PHP, Swift, Ruby, JQuery, HTML, CSS. You won't find anything less common like Haskell, Erlang, Elixir, Common Lisp, Scheme, Clojure, Rust, etc.
Con Limited usefulness for intermediate or experienced programmers
No advanced coding challenges. Look for those on other sites like hackerrank.