Loading collection data...
Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
'in' is wrong in this case, you only want to check the last character. And yes, endswith should be faster, it only checks the end of the string ('in' will check the whole string).
Similar to cmgerber's suggestion, an option in "Your Next Challenge..." to only suggest katas I didn't complete would be great.