gistfile1.py

#-------------------------------------------------
# imports
#-------------------------------------------------
import sys
import random
from pprint import pprint

#-----------------------------------------------
# read file in, validate even number of players
#-------------------------------------------------
filename = sys.argv[1]
names = [name.strip() for name in open(filename)]
if len(names)%2 != 0:
        sys.exit("need even number of players")

#-------------------------------------------------
#
#-------------------------------------------------
family_dict = {}
for name in names:
        first_name, last_name = name.split()
        if last_name not in family_dict:
                family_dict[last_name] = []
        family_dict[last_name].append(first_name)

pairs = []
while len(family_dict) > 0:
        #get the largest family so we don't end up with two members of the same family left at the end
        largest_family=sorted(family_dict, key=lambda k: len(family_dict[k]), reverse=True).pop(0)

        #get a random family that is NOT the largest family
        sample = family_dict.keys()
        sample.remove(largest_family)
        random_family=random.choice(sample)

        #get two players from the two families
        player1 = random.choice(family_dict[largest_family])
        player2 = random.choice(family_dict[random_family])
        pairs.append([player1+" "+largest_family, player2+" "+random_family])
        #remove the two players from the dictionary
        family_dict[largest_family].remove(player1)
        family_dict[random_family].remove(player2)
        if len(family_dict[largest_family]) == 0:
                del family_dict[largest_family]
        if len(family_dict[random_family]) == 0:
                del family_dict[random_family]


print pairs