`str.format` allows the format string to navigate through indexes, entries, and attributes. If the result of the formatting is echoed back and any non-trivial o

`str.format` allows the format string to navigate through indexes, entries, and attributes. If the result of the formatting is echoed back and any non-trivial object it passed in, it allows for all sorts of introspection. printf-style... does not support any of that. It can only format the objects passed in.