#! /usr/bin/python

# "secret santa" gift pairs: sets of spouses, who buys for who?
# can't have a spouse buying for spouse, and can't have person
# buy for self.
# brute force algorithm below is probably easiest. With only
# a few values, performance doesn't matter, so this worked ok,
# but I think that probably setting them up as disjoint sets or
# just a dictionary/mapping with a key for each user and
# possible matchups as a list as the value and then just
# randomizing would be faster.

import pprint, random

pairs = (('joe', 'sandy'),
 ('michael', 'cheryl'),
 ('jamieson', 'jennifer'),
 ('matthew', 'dannii'))
# convert to straight list
all = " ".join([" ".join(pair) for pair in pairs]).split()

def randomize_sample(sample):
    while True:
        newsample = zip(random.sample(sample, len(sample)),random.sample(sample,len(sample)))
        if [(a,b) for a,b in newsample if a==b]:
            # skip this matchup, someone is buying for themselves
            continue
        if [pair for pair in newsample if pair in pairs]:
            # skip this matchup, someone has their spouse
            continue
        if [(a,b) for (a,b) in newsample if (b,a) in pairs]:
            # skip this matchup, someone has their spouse (reversed pair)
            continue
        # we made it this far, this sample is ok!
        break
    return newsample

for i in xrange(10):
    sample = randomize_sample(all)
    print "\n%s:\n" % (i+1) +  "\n".join([": ".join(pair) for pair in sample])