In [1]:

    

from math import pi

def vol_sphere(r):
    if r<0:
        print('Radius must be greater than zero')
        return
    else:
        return (4/3)*pi*r**3


    

In [2]:

    

vol_sphere(4)


    

    
Out[2]:





268.082573106329

In [3]:

    

vol_sphere(-1)


    

    




Radius must be greater than zero

In [4]:

    

vol_sphere(0)


    

    
Out[4]:





0.0

In [ ]: