Ranked Choice Voting script

rcv.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import sys
import json

def tally(voters):
    results = {}
    for votes in voters.itervalues():
        if votes:
            choice = votes[0]
            count = results[choice] if choice in results else 0
            results[choice] = count + 1
    return results

with open('votes.json') as f:
    voters = json.load(f)

round = 1
winner = False
while not winner:
    print 'Round {}'.format(round)
    results = tally(voters)
    if not results:
        print '\nAll choices eliminated'
        print 'No winner...'
        break

    high = -1
    low = sys.maxsize
    lead = ''
    for choice, count in results.iteritems():
        if count > high:
            lead = choice
            high = count
        low = min(low, count)
        perc = float(count) / float(len(voters))
        print '  {} - {} votes {:.1%}'.format(choice, count, perc)

    perc = float(results[lead]) / float(len(voters))
    if perc > 0.5:
        print '\n{} is the Winner!'.format(lead)
        winner = True
    elif len(results) == 2:
        print '\nTie!'
        winner = True
    else:
        print '\nNo winner'
        elim = [choice for choice, count in results.iteritems() if count <= low]
        for votes in voters.itervalues():
            if votes[0] in elim:
                votes.pop(0)
        for voter, votes in voters.items():
            if not votes:
                del voters[voter]
    round += 1
    print

votes.json

{
    "trevor":
    [
        "Hitchhiker's Guide to the Galaxy",
        "Jurassic Park",
        "The Martian",
        "A Game of Thrones",
        "The Gunslinger",
        "Ender's Game"
    ],
    "duane":
    [
        "Hitchhiker's Guide to the Galaxy",
        "A Game of Thrones",
        "The Martian",
        "Ancillary Justice",
        "The Gunslinger",
        "Ender's Game",
        "Jurassic Park"
    ],
    "kyle":
    [
        "A Game of Thrones",
        "Hitchhiker's Guide to the Galaxy",
        "The Martian",
        "Ancillary Justice",
        "The Gunslinger",
        "Ender's Game",
        "Jurassic Park"
    ],
    "thomas":
    [
        "Ancillary Justice",
        "Ender's Game",
        "The Martian",
        "Hitchhiker's Guide to the Galaxy",
        "The Gunslinger",
        "Jurassic Park",
        "A Game of Thrones"
    ],
    "zach":
    [
        "A Game of Thrones",
        "Hitchhiker's Guide to the Galaxy",
        "Ender's Game",
        "Ancillary Justice"
    ],
    "ani":
    [
        "Ancillary Justice",
        "A Game of Thrones",
        "Hitchhiker's Guide to the Galaxy",
        "The Martian",
        "The Gunslinger",
        "Ender's Game",
        "Jurassic Park"
    ],
    "sayalee":
    [
        "A Game of Thrones",
        "Ancillary Justice",
        "Hitchhiker's Guide to the Galaxy",
        "The Martian",
        "The Gunslinger",
        "Ender's Game",
        "Jurassic Park"
    ],
    "tolunay":
    [
        "The Martian",
        "A Game of Thrones",
        "Ancillary Justice",
        "Hitchhiker's Guide to the Galaxy",
        "Ender's Game",
        "The Gunslinger",
        "Jurassic Park"
    ],
    "tave":
    [
        "Ancillary Justice",
        "Hitchhiker's Guide to the Galaxy",
        "The Martian",
        "The Gunslinger",
        "Ender's Game",
        "A Game of Thrones",
        "Jurassic Park"
    ]
}