from math import pi


class Esfera:
    def __init__(self, centre, radi):
        self.centre = centre
        self.radi = radi

    def __str__(self):
        return "Esfera de centre {:s} i radi {:.1f}".format(
            str(self.centre), self.radi)

    def volum(self):
        return 4 / 3 * pi * self.radi ** 3