Actually Python does explicitly reject strings. >>> sum(['hello', ' world'], '') TypeError: sum() can't sum strings [use ''.join(seq) instead] But this is

Actually Python does explicitly reject strings. >>> sum(['hello', ' world'], '') TypeError: sum() can't sum strings [use ''.join(seq) instead] But this is done explicitly against strings. They would _just work_ if not for this restriction, because based on usage they should work.