Create child class of Python dict with modified values

[dmitrey]

hi all,
suppose I have defined a child class of Python dict, currently it
constructor looks like that:
    def __init__(self, *args, **kwargs):
        dict.__init__(self, *args, **kwargs)
        #(+some more insufficient code)

Constructor should be capable of calling with either any way Python
dict is constructed or with a Python dict instance to be derived from;
calculations speed is important.

So it works well for now, but I want __init__ to set modified values,
like this:
values_of_the_dict = [some_func(elem) for elem in self.values()]

How this could be done?

Thank you in advance,
Dmitrey.