class SuperString(str):
    def __init__(self, sourcestr):
        print(self)
        super().__init__(self, sourcestr.upper())
s = SuperString('mystring')
print(s)

class SuperString(str):
    def __new__(cls, arg):
        return super().__new__(cls, arg.upper())

class Ts(object):
    def __init__(self,s):
        self.s=s
    def __str__(self):
        return self.s
class Tss(Ts):
    def __init__(self,s):
        super(Tss,self).__init__(s.upper())
a=Tss("asda")
>>> print a
ASDA