How does solution show here if it cannot run here?

This solution was posted when Python 2 was available. After Python 2 was removed this solution should become invalid, but for some kata, especially when it has really many solutions, some can survive invalidation process. They will be gradually disappearing though.

Also why we need to mark a comment spoiler when discussing on a thread under a solution already out there?

Home page dashboard displays all posts, even posted under solutions one cannot see.

That's a Python 2.7 solution, read the comment in the solution or the posts below, and don't forget to mark your post as having spoiler content next time, please.