I thought that was the reason - but if I give the wrong types, it won't work. Often, I can infer the types myself, but why not just tell me? I think there are conventions, like "it's a string or a number unless stated otherwise", and these defaults work great. You just need a little faith in the library writer.

For example, xmlrpclib.ServerProxy takes an URI - is that a string or a special URI object? I guess it's most convenient if it's just a string, but if you had just constructed the URI by concatenating the separate parts, it's inefficient to immediately parse them apart - and so Java has URI objects. Maybe it's just that Python admits it's a scripting language, and uses machine cycles to serve you - instead of the other way round. That's a nice idea.