Generate single-direction pairs of people for secret santa (i.e. A sends to B, but not B sends to A).

secret_santa.py

"""
Secret santa matching attempt
"""

import random

"""
Match people randomly to others, for example in a secret santa
Takes a list of people as an input and returns a list of tuples (person a sending to person b)
"""
def secret_santa(people):
    # This list holds the positions in the people list of people who haven't been matched
    people_indexes = range(0, len(people))
    # Our matches list
    matches = []

    if len(people_indexes) < 2:
        raise Exception("You can't have a secret santa with one person!")
        # and it won't be a very good one with two people either ;)

    # Let's pair people up!
    current = 0
    while len(people_indexes) > 0:
        # The position of the current unmatched person in people
        current_index = people_indexes[current]
        
        # If we're on our last person join them up with the first person
        if len(people_indexes) == 1:
            matches.append((people[current_index], matches[0][0]))
            break

        # Get the next person - remove the current person's position and select a random position
        people_indexes.pop(current)    
        next = random.randrange(0, len(people_indexes))
        
        # The position of the next unmatched person in people
        next_index = people_indexes[next]

        # Add the match to our matches list and set current to be the next person
        matches.append((people[current_index], people[next_index]))    
        current = next
    
    return matches
    
print secret_santa(["Ross", "Paul", "Rich", "Santa", "Elf", "David Attenborough", "The Lich King"])