dict elements are sometimes treated as List and sometimes as String

[deanhystad]

If you want the dictionary to contain lists you need to add lists. "coat" is a string. ["coat"] is a list that contains a string. You can append to a list of strings. You cannot append to a string. Your first two examples run correctly because they initially add a list to the dictionary. The final example fails because it adds a word. I think you problem is a typo.