assign_houses.py

import random

players = ['Garry', 'Joanna', 'Sara', 'Mark', 'Phil', 'Tom']
houses = ['Stark', 'Greyjoy', 'Dorne', 'Tyrell', 'Lannister', 'Baratheon']

drawing = range(0, len(houses))
random.shuffle(drawing)

chosen_families = {p: houses[drawing[i]] for (i, p) in enumerate(players)}

for player, house in chosen_families.items():
    print('%(player)s is assigned house %(house)s' %
          {'player': player, 'house': house})

$ python assign_houses.py

Sara is assigned house Lannister
Phil is assigned house Dorne
Mark is assigned house Baratheon
Garry is assigned house Tyrell
Joanna is assigned house Greyjoy
Tom is assigned house Stark

Actually this is too complicated, here's a better version:

https://gist.github.com/codeweevil/1b1c7408a76b896492b5fcb432dcb8e8