By the glare of it, none. But you have to understand that ruby has that `#{}` since ways before, and python has just added that `f` syntax recently. Also in ruby it's the only way of doing string interpolation, while in python you have % and other methods.
You actually want both of these. The reason why explicitly indexed placeholder syntax is still important, even if you have interpolation, is because the order in which the arguments are referenced may change when the string is localized.
