Secret Santa

secret_santa.py

#!/usr/bin/env python3
from random import shuffle

people = [
    "Jānis", 
    "Ilze", 
    "Kristaps", 
    "Elīza", 
    "Alberts", 
    "Anna", 
    "Ēvalds", 
    "Lāsma", 
    "Imants", 
    "Alise", 
    "Roberts",
    "Emīlija",
    "Mārtiņš",
    "Līga",
    "Miķelis"
]

forbiddenPairs = {
    ("Jānis", "Ilze"), 
    ("Imants", "Emīlija"),
    ("Ēvalds", "Līga"),
}

givers = people[:]
recipients = people[:]
shuffle(recipients)

def isValidPair(giver, recipient):
    if (
        giver == recipient or 
        (giver, recipient) in forbiddenPairs or 
        (recipient, giver) in forbiddenPairs
        ):
        return False
    else:
        return True

def pairUp(originalGivers, originalRecipients, attempts = 50):
    givers = originalGivers[:]
    recipients = originalRecipients[:]

    failureCounter = 0
    pairs = []

    while givers:
        giver = givers[0]
        givers.remove(giver)

        while True:
            recipient = recipients[0]
            recipients.remove(recipient)

            if isValidPair(giver, recipient):
                pairs += [(giver, recipient)]
                failureCounter = 0
                break
            elif failureCounter > len(recipients):
                pairs = None
                givers = []
                recipients = []
                break;
            else:
                failureCounter += 1
                recipients += [recipient]

    if pairs:
        return pairs
    elif attempts > 0:
        shuffle(originalRecipients)
        return pairUp(originalGivers, originalRecipients, attempts - 1)
    else:
        return None


if __name__ == '__main__':
    pairs = pairUp(givers, recipients)

    if pairs:
        for (giver, recipient) in pairs:
            print("{} dāvina dāvanu {}".format(giver, recipient))
    else:
        print("Neizdevās sapārot davinātājus.")