BasicExercise 03.py

#!/usr/bin/env python2.6
#_*_coding: utf8_*_ 

from math import *

def volumen(r): 
   v = (4.0/3.0)*pi*(r**3)
   print "El volumen es:"+ str(v)


rad = eval (raw_input ("Introduzca el valor de R:"))

  print "No sea bruto el radio debe ser positivo"

else:
  volumen(rad)