class XFunction():
    def __call__(self, *args):
        return self.f(*args)

    def __mul__(self, number):
        def new_f(*args):
            return number*self.f(*args)
        return XFunction(new_f)

    def __rmul__(self, number):
        return self.__mul__(number)

    def __init__(self, f):
        self.f = f

if __name__ == "__main__":
    xfunc = XFunction(lambda x: x)
    assert xfunc(1)==1

    yfunc = 2*xfunc
    assert yfunc(1) ==2