class Ballot(models.Model):
"""For example, a ballot for ASHMC President would have
candidates (actually PersonCandidates).
Multiple ballots can appear in a measure; that is,
you can have a ballot for ASHMC President election and
one for VP election in the same measure.
"""
VOTE_TYPES = Utility.enum('POPULARITY',
'PREFERENCE',
'SELECT_X',
'INOROUT',
type_name='BallotVoteType')
TYPES = (
(VOTE_TYPES.POPULARITY, "Popularity"),
(VOTE_TYPES.PREFERENCE, 'Preference'),
(VOTE_TYPES.SELECT_X, 'Select Top X'),
(VOTE_TYPES.INOROUT, 'Yes or No'),
)
vote_type = models.SmallIntegerField(default=0, choices=TYPES)
number_to_select = models.PositiveIntegerField(blank=True, null=True)
measure = models.ForeignKey('Measure', null=True)
display_position = models.IntegerField(default=1)
title = models.CharField(max_length=50)
blurb = models.TextField()
can_write_in = models.BooleanField(default=False)
can_abstain = models.BooleanField(default=True)
is_secret = models.BooleanField(default=False)
is_irv = models.BooleanField(
default=False,
help_text=
'Only applies to Preferential type; changes the way winners are calculated.',
)
def get_winners(self):
"""does not break ties."""
if self.candidate_set.count() == 0:
return []
if self.vote_type == self.VOTE_TYPES.POPULARITY or self.vote_type == self.VOTE_TYPES.INOROUT:
max_choices = max(
self.candidate_set.annotate(
pv_max=models.Count('popularityvote')).values_list(
'pv_max', flat=True))
return self.candidate_set.annotate(
models.Count('popularityvote')).filter(
popularityvote__count=max_choices)
elif self.vote_type == self.VOTE_TYPES.PREFERENCE:
if not self.is_irv:
# The lower the sum of the ranks of a candidate, the better they're doing overall.
min_choices = min(
self.candidate_set.annotate(pf_sum=models.Sum(
'preferentialvote__amount')).values_list('pf_sum',
flat=True))
return self.candidate_set.annotate(
models.Sum('preferentialvote__amount')).filter(
preferentialvote__amount=min_choices)
# IRV voting is a little more intense.
# we do rounds - until one candidate has a majority, we eliminate the
# least popular candidate and apply the voters' other votes to their
# next favorite choice.
# http://en.wikipedia.org/wiki/Instant-runoff_voting
# Since each candidate gets a vote with a different ballot,
# we normalize the number of votes by the number of voters --
# each voter should have contributed the same number of votes per
# ballot (e.g., the number of candidates on the ballot)
# If no more votes can come in, then don't calculate again.
# Don't do anything while votes can still come in.
if not self.measure.voting_closed:
return Candidate.objects.none()
# Don't re-calculate if it's been calculated.
if InstantRerunVotingRound.objects.filter(
ballot=self).count() != 0:
irvr = InstantRerunVotingRound.objects.filter(
ballot=self).order_by('-number')[0]
try:
max_votes = max(
IRVCandidate.objects.filter(irv_round=irvr, ).annotate(
models.Count('votes')).values_list(
'votes__count',
flat=True,
))
return irvr.irvcandidate_set.annotate(
models.Count('votes')).filter(votes__count=max_votes)
except ValueError:
return IRVCandidate.objects.none()
logger.debug("Calcluating IRV for BALLOT %s", self)
total_votes = self.measure.vote_set.count()
candidates = list(self.candidate_set.all())
logger.debug("total votes: %s", total_votes)
the_round = InstantRerunVotingRound.objects.create(
number=1,
ballot=self,
)
for candidate in candidates:
logger.debug("Creating initial IRVCandidate for %s", candidate)
irvc = IRVCandidate.objects.create(
candidate=candidate,
irv_round=the_round,
# Get the FIRST-CHOICE votes for every candidate.
)
irvc.votes.add(*list(
self.preferentialvote_set.filter(
candidate=candidate,
amount=1,
)))
# Do rounds until *someone* has a majority.
logger.debug("calculating starting max votes")
try:
max_votes = max(
IRVCandidate.objects.filter(
irv_round=the_round, ).annotate(
models.Count('votes')).values_list(
'votes__count',
flat=True,
))
logger.debug("max_votes: %s", max_votes)
except ValueError:
Candidate.objects.none()
while max_votes <= total_votes / 2:
logger.debug("%s out of %s", max_votes, total_votes)
old_candidates = IRVCandidate.objects.filter(
irv_round=the_round).annotate(
pv_count=models.Count('votes')).order_by('pv_count')
logger.debug("old candidates: %s", old_candidates)
the_round = InstantRerunVotingRound.objects.create(
ballot=self,
number=the_round.number + 1,
)
logger.debug("creating new round: %s", the_round.number)
# TODO: break ties LOLOLOL
loser = old_candidates[0]
logger.debug("found loser: %s", loser)
# Move all the surviving votes over, and delete the
# loser from the running.
for irvcandidate in old_candidates[1:]:
irvc = IRVCandidate.objects.create(
irv_round=the_round,
candidate=irvcandidate.candidate,
)
irvc.votes.add(*list(irvcandidate.votes.all()))
# Attach losers votes to their next preference
for pvote in loser.votes.all():
logger.debug("attaching loser's votes to other candidates")
v = pvote.vote
try:
next_pvote = v.preferentialvote_set.get(
amount=pvote.amount + 1, )
except PreferentialVote.ObjectDoesNotExist:
logger.info(
"losing a preference due to lack of ranking")
# If there are no more preferences, that's fine.
# their vote no longer contributes to the total,
# and they don't get a candidate assigned to them.
total_votes -= 1
continue
next_irc = IRVCandidate.objects.get(
irv_round=the_round,
candidate=next_pvote.candidate,
)
next_irc.votes.add(next_pvote)
max_votes = max(
IRVCandidate.objects.filter(
irv_round=the_round, ).annotate(
models.Count('votes')).values_list('votes__count',
flat=True))
# The rounds are over! Time to find the max votes and return the list
# of winners.
return IRVCandidate.objects.annotate(models.Count('votes')).filter(
votes__count=max_votes, irv_round=the_round)
elif self.vote_type == self.VOTE_TYPES.SELECT_X:
max_choices = self.candidate_set.annotate(pv_max=models.Count(
'popularityvote')).order_by('-pv_max').values_list(
'pv_max', flat=True)[0]
return self.candidate_set.annotate(
models.Count('popularityvote')).filter(
popularityvote__count=max_choices)
def ordered_candidates(self):
if self.vote_type == self.VOTE_TYPES.POPULARITY or self.vote_type == self.VOTE_TYPES.INOROUT:
return self.candidate_set.annotate(
votes=models.Count('popularityvote')).order_by('-votes')
elif self.vote_type == self.VOTE_TYPES.PREFERENCE:
return self.candidate_set.annotate(
votes=models.Sum('preferentialvote__amount')).order_by('votes')
elif self.vote_type == self.VOTE_TYPES.SELECT_X:
return self.candidate_set.annotate(
votes=models.Count('popularityvote')).order_by('-votes')
def __unicode__(self):
return u"Ballot #{}: {}".format(self.id, self.title)
class Meta:
unique_together = (('measure', 'title'), )
def save(self, *args, **kwargs):
if self.vote_type == self.VOTE_TYPES.SELECT_X and self.number_to_select is None:
raise IntegrityError(
"Can't have a SELECT_X vote type and no number_to_select.")
super(Ballot, self).save(*args, **kwargs)
if self.vote_type == self.VOTE_TYPES.INOROUT:
# create the two candidates now.
yes, _ = Candidate.objects.get_or_create(
title="Yes",
ballot=self,
)
no, _ = Candidate.objects.get_or_create(
title="No",
ballot=self,
)
class Ballot(models.Model):
"""For example, a ballot for ASHMC President would have
candidates (actually PersonCandidates).
Multiple ballots can appear in a measure; that is,
you can have a ballot for ASHMC President election and
one for VP election in the same measure.
"""
VOTE_TYPES = Utility.enum('POPULARITY',
'PREFERENCE',
'SELECT_X',
'INOROUT',
type_name='BallotVoteType')
TYPES = (
(VOTE_TYPES.POPULARITY, "Popularity"),
(VOTE_TYPES.PREFERENCE, 'Preference'),
(VOTE_TYPES.SELECT_X, 'Select Top X'),
(VOTE_TYPES.INOROUT, 'Yes or No'),
)
vote_type = models.SmallIntegerField(default=0, choices=TYPES)
number_to_select = models.PositiveIntegerField(blank=True, null=True)
measure = models.ForeignKey('Measure', null=True)
display_position = models.IntegerField(default=1)
title = models.CharField(max_length=50)
blurb = models.TextField()
can_write_in = models.BooleanField(default=False)
can_abstain = models.BooleanField(default=True)
is_secret = models.BooleanField(default=False)
def get_winners(self):
"""does not break ties."""
if self.vote_type == self.VOTE_TYPES.POPULARITY or self.vote_type == self.VOTE_TYPES.INOROUT:
max_choices = max(
self.candidate_set.annotate(
pv_max=models.Count('popularityvote')).values_list(
'pv_max', flat=True))
return self.candidate_set.annotate(
models.Count('popularityvote')).filter(
popularityvote__count=max_choices)
elif self.vote_type == self.VOTE_TYPES.PREFERENCE:
# The lower the sum of the ranks of a candidate, the better they're doing overall.
min_choices = min(
self.candidate_set.annotate(
pf_sum=models.Sum('preferentialvote__amount')).values_list(
'pf_sum', flat=True))
return self.candidate_set.annotate(
models.Sum('preferentialvote__amount')).filter(
preferentialvote__amount=min_choices)
elif self.vote_type == self.VOTE_TYPES.SELECT_X:
max_choices = self.candidate_set.annotate(pv_max=models.Count(
'popularityvote')).order_by('-pv_max').values_list(
'pv_max', flat=True)[0]
return self.candidate_set.annotate(
models.Count('popularityvote')).filter(
popularityvote__count=max_choices)
def ordered_candidates(self):
if self.vote_type == self.VOTE_TYPES.POPULARITY or self.vote_type == self.VOTE_TYPES.INOROUT:
return self.candidate_set.annotate(
votes=models.Count('popularityvote')).order_by('-votes')
elif self.vote_type == self.VOTE_TYPES.PREFERENCE:
return self.candidate_set.annotate(
votes=models.Sum('preferentialvote__amount')).order_by('votes')
elif self.vote_type == self.VOTE_TYPES.SELECT_X:
return self.candidate_set.annotate(
votes=models.Count('popularityvote')).order_by('-votes')
def __unicode__(self):
return u"Ballot #{}: {}".format(self.id, self.title)
class Meta:
unique_together = (('measure', 'title'), )
def save(self, *args, **kwargs):
if self.vote_type == self.VOTE_TYPES.SELECT_X and self.number_to_select is None:
raise IntegrityError(
"Can't have a SELECT_X vote type and no number_to_select.")
super(Ballot, self).save(*args, **kwargs)
if self.vote_type == self.VOTE_TYPES.INOROUT:
# create the two candidates now.
yes, _ = Candidate.objects.get_or_create(
title="Yes",
ballot=self,
)
no, _ = Candidate.objects.get_or_create(
title="No",
ballot=self,
)