>>> from punt3D import Punt3D
>>> from pilota import Pilota

--ini-enunciat

>>> p = Punt3D(0, 0, 0)
>>> print(str(p))
(0.0, 0.0, 0.0)
>>> c = Pilota(1.0, p, 3.5, 'vermell')
>>> print(str(c))
Pilota de centre (0.0, 0.0, 0.0) i radi 1.0
>>> print('{:.2f}'.format(c.volum()))
4.19
>>> c.color
'vermell'
>>> print('{:.2f}'.format(c.pes))
3.50
>>> print('{:.2f}'.format(c.densitat()))
0.84

--fi-enunciat

>>> c.pes = 10.0
>>> print('{:.2f}'.format(c.densitat()))
2.39