Hi @codesilas and welcome to Codewars - it seems this is your first kata: on Codewars you must return your final result, rather than just print it to console.

So replace your current print(new_list) with the return statement: return new_list. That's why the tests are saying None should equal ['as', 'df', 'ad', 'sf'] -- this error message means that you are not returning anything, hence the None, while the tests are expecting the list ['as', 'df', 'ad', 'sf'].

I recommend reading https://docs.codewars.com/getting-started/solving-kata and also this Troubleshooting guide as you start out with the site, as Chrono79 said - it contains lots of helpful info.

Read this: https://docs.codewars.com/training/troubleshooting/#expected-the-same