Strings should never be returned from functions especially general purpose functions.
I'm not sure what angle brackets do for creating an array but it's not wise to use extremely obscure features when providing support on these forums unless it's the only way to do it.
containi() returns the position in the string where the search string starts. If it is not found, it will return -1. So "~containi()" will evaluate as True when the string is NOT found and when the string does not start at the beginning.