import math as m
class Sirkel:

    def __init__(self, radius):
        self._radius = radius

    def diameter(self):
        return self._radius * 2

    def omkrets(self):
        return self.diameter() * m.pi

    def areal(self):
        return m.pi * self._radius**2

    def __str__(self):
        return (f"Jeg er en sirkel med radius {self._radius}")

def hovedprogram():
    s1 = Sirkel(3)
    s2 = Sirkel(4.2)

    #print(s1.omkrets())
    #print(s1.areal())

    #print(s2.diameter())

    print(s1)
    print(s2)
hovedprogram()