Can I write type converters for a custom class?

I want to write a method in my custom classes to return string representations of instantiated objects (similar to writing a "__str__" method in Python), to allow calls such as sprintf('%s', object). The next best solution is to just write a "toString" method for each of my classes, but of course I would have to maintain that function name for all my classes to make the code usable. I appreciate any other ideas.