# 1001.py 

def genitore (x,y): return padre(x,y) or madre(x,y)

def nonno (x,z):
  return any(padre(x,y) and genitore(y,z) for y in Mondo)

def madre (x,y):
  return x=='anna' and y in ['piero','maria'] \
    or x=='lisa' and y=='giulia' or x=='maria' and y=='elena' \
    or x=='monica' and y=='alfonso'

def padre (x,y):
  return (x=='giovanni' and y in ['maria','piero']
    or x=='piero' and y=='giulia'
    or x=='federico' and y=='alfonso'
    or x=='alfonso' and y=='elena')

def cercanonni (a):
  print (list(filter(lambda x: nonno(x,a),Mondo)))

def cercaunnonno (a):
  for x in Mondo:
    if nonno(x,a): print(x); return
  print('Non trovato.')

Mondo=['alfonso','anna','elena','federico','giovanni',
    'giulia','lisa','maria','monica','piero']

cercaunnonno('elena')
# federico

cercanonni('elena')
# ['federico', 'giovanni']