[Python-Dev] What if replacing items in a dictionary returns the new dictionary?

[Roy Hyunjin Han]

>   You can implement this in your own subclass of dict, no?

Yes, I just thought it would be convenient to have in the language
itself, but the responses to my post seem to indicate that [not
returning the updated object] is an intended language feature for
mutable types like dict or list.

class ReplaceableDict(dict):
    def replace(self, **kw):
        'Works for replacing string-based keys'
        return dict(self.items() + kw.items())