No, no such built-in method exists for lists. It is trivial to find out if a list index is valid, so no function is needed. You could just put the code in your function (or the even more readable s[ind] if ind < len(s) else 0) directly into the two or three places it's needed, and it would be perfectly understandable.
(Of course your code assumes ind is always positive...)
If you do want to write a function, make it a method of a list subclass.
