Hi!

I thought that maybe dict could accept several mappings as positional arguments, like this:

class Dict4(dict):
    def __init__(self, *args, **kwargs):
        if len(args) > 1:
            if not all([isinstance(arg, dict) for arg in args]):
                raise TypeError('Dict4 expected instances of dict since multiple positional arguments were passed')

            temp = args[0].copy()

            for arg in args[1:]:
                temp.update(arg)

            super().__init__(temp, **kwargs)
        else:
            super().__init__(*args, **kwargs)

AFAIK, this wouldn't create compatibility problems, since you can't pass two positional arguments now anyways.

It would be useful to solve the "sum/union dicts" discussion, for example: requests.get(url, params=dict(params, {'foo': bar})

Whar are your thoughts?