Comment by vitus

> The only thing that can sometimes bite you here is that str is iterable, if you expect a list of str and you only get a str and suddenly you iterate over the chars.

Python isn't even unique in this regard! You can iterate over a string whether you're working in JavaScript, C++, or Go. (And that's not even getting into cases like Haskell where String is merely syntactic sugar for [Char].)