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Concise STV #6

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Concise STV #6

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a329fa4
docstring and pep8 fixes
user2589 Mar 13, 2018
e65de95
fix expected winners in a docstring
user2589 Mar 14, 2018
ef222f0
conscise reimplementation of STV
user2589 Mar 14, 2018
a82e410
adjustable NC name
user2589 Mar 14, 2018
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177 changes: 27 additions & 150 deletions election.py
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@
__status__ = "Production"


class Candidate:
class Candidate(object):
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old style classes might cause issues on some platforms

"""Candidate with a name and unique identifier.

Attributes:
Expand All @@ -21,50 +21,20 @@ class Candidate:
"""

def __init__(self, uid, name=None):
"""Initializes Candidate with name and uid.
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standard methods don't really need docstrings


Args:
uid: String representing the unique identifier of the Candidate.
Used for equality, hashing, and ordering in a random tiebreak.
name: String representing the name of the Candidate.
"""
self.uid = uid
self.name = name

def __eq__(self, other):
"""Checks equality between two Candidates using uids.

Args:
other: Candidate to check equality with.

Returns:
Boolean indicating if the Candidates are equal or not.
"""
if isinstance(other, Candidate):
return self.uid == other.uid

def __hash__(self):
"""Returns the hash value of the Candidate.

Returns:
Integer hash value of the Candidate.
"""
return hash(self.uid)

def __repr__(self):
"""Returns a printable system representation of the Candidate.

Returns:
String containing the printable representation of the Candidate.
"""
return 'Candidate({!r}, name={!r})'.format(self.uid, self.name)

def __str__(self):
"""Returns a printable user representation of the Candidate.

Returns:
String containing the printable representation of the Candidate.
"""
return '{} ({})'.format(self.uid, self.name
if self.name is not None else self.uid)

Expand All @@ -78,20 +48,14 @@ class NoConfidence(Candidate):
"""

def __init__(self):
"""Initializes NoConfidence."""
self.uid = 'NC'
self.name = 'No Confidence'

def __repr__(self):
"""Returns a printable system representation of NoConfidence.

Returns:
String containing the printable representation of NoConfidence.
"""
return 'NoConfidence()'


class Ballot:
class Ballot(object):
"""Ballot consisting of ranked candidates and a vote value

The vote value of the ballot is awarded to the most preferred candidate that
Expand All @@ -118,25 +82,12 @@ def __init__(self, candidates=None, starting_rank=0, vote_value=1.0):
self._preferred_active_rank = starting_rank

def __eq__(self, other):
"""Checks equality between two Ballots.

Args:
other: Ballot to check equality with.

Returns:
Boolean indicating if the Ballots are equal or not.
"""
if isinstance(other, Ballot):
return (self.candidates == other.candidates and
self.vote_value == other.vote_value and
self._preferred_active_rank == other._preferred_active_rank)

def __repr__(self):
"""Returns a printable system representation of the Ballot.

Returns:
String containing the printable representation of the Ballot.
"""
return 'Ballot(candidates={!r}, vote_value={!r}, starting_rank={!r})'.format(
self.candidates, self.vote_value, self._preferred_active_rank)

Expand Down Expand Up @@ -196,7 +147,7 @@ def set_candidates(self, candidates):
self._preferred_active_rank = 0


class VoteTracker:
class VoteTracker(object):
"""Vote Tracker for assigning votes to Candidates.

Attributes:
Expand All @@ -205,44 +156,24 @@ class VoteTracker:
"""

def __init__(self, votes_cast=0.0, votes_for_candidate=None):
"""Initializes VoteTracker with votes cast and votes for candidates.

Args:
votes_cast: Float value of the total votes cast.
votes_for_candidate: Dict mapping Candidates to float values of
votes.
"""
self.votes_cast = votes_cast
self._votes_for_candidate = (votes_for_candidate
if votes_for_candidate is not None else dict())

def __eq__(self, other):
"""Checks equality between two VoteTrackers.

Args:
other: VoteTracker to check equality with.

Returns:
Boolean indicating if the VoteTrackers are equal or not.
"""
if isinstance(other, VoteTracker):
return (self.votes_cast == other.votes_cast and
self._votes_for_candidate == other._votes_for_candidate)

def __repr__(self):
"""Returns a printable system representation of the VoteTracker.

Returns:
String containing the printable representation of the VoteTracker.
"""
return 'VoteTracker(votes_for_candidate={!r}, votes_cast={!r})'.format(
self._votes_for_candidate, self.votes_cast)

def decription(self):
"""Returns a printable long-form user representation of the VoteTracker.

Returns:
String containing the printable representation of the VoteTracker.
:return String containing the printable representation of the
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There is a standard for autodocumentation:
https://thomas-cokelaer.info/tutorials/sphinx/docstring_python.html

VoteTracker.
"""
description = 'VoteTracker for {} votes:'.format(self.votes_cast)
for candidate in sorted(self._votes_for_candidate, key=self._votes_for_candidate.get, reverse=True):
Expand All @@ -252,9 +183,8 @@ def decription(self):
def cast_vote_for_candidate(self, candidate, vote_value):
"""Casts the vote for the Candidate, updating the stored vote totals.

Args:
candidate: Candidate to receive the vote.
vote_value: Float value of the vote.
:param candidate: Candidate to receive the vote.
:param vote_value: Float value of the vote.
"""

if candidate is None:
Expand All @@ -278,31 +208,26 @@ def cast_vote_for_candidate(self, candidate, vote_value):
def votes_for_candidate(self, candidate):
"""Returns the value of the votes for the given Candidate.

Args:
Candidate: Candidate to obtain the vote value.
:param candidate: Candidate to obtain the vote value.

Returns:
Float value of the votes for the Candidate.
:return Float value of the votes for the Candidate.
"""
return self._votes_for_candidate.get(candidate, 0.0)

def candidates(self):
"""Returns the Candidate(s) being tracked.

Returns:
Set of candidates being tracked.
:return Set of candidates being tracked.
"""
return set(self._votes_for_candidate.keys())

def candidates_reaching_threshold(self, candidates, threshold):
"""Returns the Candidate(s) with vote values meeting the threshold.

Args:
candidates: Set of Candidates to check.
threshold: Float value of the vote threshold.
:param candidates: Set of Candidates to check.
:param threshold: Float value of the vote threshold.

Returns:
Set of Candidates meeting the vote threshold.
:return Set of Candidates meeting the vote threshold.
"""
candidates_reaching_threshold = set()

Expand All @@ -316,11 +241,9 @@ def candidates_reaching_threshold(self, candidates, threshold):
def candidates_with_fewest_votes(self, candidates):
"""Returns the Candidate(s) with the fewest votes.

Args:
candidates: Set of Candidates to check.
:param candidates: Set of Candidates to check.

Returns:
Set of Candidates with the fewest votes.
:return Set of Candidates with the fewest votes.
"""
candidates_with_fewest_votes = set()
fewest_votes = -1
Expand All @@ -338,7 +261,7 @@ def candidates_with_fewest_votes(self, candidates):
return candidates_with_fewest_votes


class ElectionRound:
class ElectionRound(object):
"""Election data for a round of voting.

Attributes:
Expand All @@ -353,28 +276,13 @@ class ElectionRound:
def __init__(self, candidates_elected=None, candidates_eliminated=None,
threshold=0, random_tiebreak_occurred=False,
vote_tracker=None):
"""Initializes ElectionRound with threshold, Candidate, and vote data.

Args:
candidates_elected: Set of Candidates elected in this round.
candidates_eliminated: Set of Candidates eliminated in this round.
threshold: Float value of the vote threshold to be elected.
random_tiebreak_occured: Boolean indicating if a random tiebreak
occurred or not in this round.
vote_tracker: VoteTracker for counting votes in this round.
"""
self.threshold = threshold
self.candidates_elected = (candidates_elected if candidates_elected is not None else set())
self.candidates_eliminated = (candidates_eliminated if candidates_eliminated is not None else set())
self.random_tiebreak_occurred = random_tiebreak_occurred
self.vote_tracker = (vote_tracker if vote_tracker is not None else VoteTracker())

def __repr__(self):
"""Returns a printable system representation of the ElectionRound.

Returns:
String containing the printable representation of the ElectionRound.
"""
return 'ElectionRound(threshold={!r}, candidates_elected={!r}, candidates_eliminated={!r}, random_tiebreak_occurred={}, vote_tracker={!r})'.format(
self.threshold, self.candidates_elected, self.candidates_eliminated, self.random_tiebreak_occurred, self.vote_tracker)

Expand Down Expand Up @@ -402,7 +310,7 @@ def description(self):
return description


class ElectionResults:
class ElectionResults(object):
"""Election results and data for all rounds.

Attributes:
Expand All @@ -418,17 +326,6 @@ class ElectionResults:
def __init__(self, ballots, candidates_elected,
election_rounds, random_alphanumeric,
seats, name=''):
"""Initializes ElectionResults with election results and data.

Args:
ballots: List of all Ballots.
candidates_elected: Set of Candidates elected.
election_rounds: List of ElectionRounds.
random_alphanumeric: String containing the random alphanumeric used
for final tiebreaks.
seats: Number of vacant seats before the election.
name: String representing the name of the election.
"""
self.ballots = ballots
self.candidates_elected = candidates_elected
self.election_rounds = election_rounds
Expand All @@ -437,22 +334,15 @@ def __init__(self, ballots, candidates_elected,
self.seats = seats

def __repr__(self):
"""Returns a printable system representation of the ElectionResults.

Returns:
String containing the printable representation of the
ElectionResults.
"""
return 'ElectionResults(name={!r}, seats={!r}, ballots={!r}, random_alphanumeric={!r}, candidates_elected={!r}, election_rounds={!r})'.format(
self.name, self.seats, self.ballots, self.random_alphanumeric, self.candidates_elected, self.election_rounds)

def description(self):
"""Returns a printable long-form user representation of the
ElectionResults.

Returns:
String containing the printable representation of the
ElectionResults.
:return String containing the printable representation of the
ElectionResults.
"""
description = 'Results for election {}:\n'.format(self.name)
if len(self.candidates_elected) > 0:
Expand All @@ -468,7 +358,7 @@ def description(self):
return description


class Election:
class Election(object):
"""Election configuration and computation.

Attributes:
Expand All @@ -486,19 +376,6 @@ class Election:

def __init__(self, ballots, seats, can_eliminate_no_confidence=True,
can_random_tiebreak=True, name='', random_alphanumeric=None):
"""Initializes Election with ballots, seats, and configuration data.

Args:
ballots: List of all Ballots.
seats: Number of vacant seats before the election.
can_eliminate_no_confidence: Boolean indicating if No Confidence may
be eliminated in the election.
can_random_tiebreak: Boolean indicating if random elimination may be
used for final tiebreaks. Otherwise, the election is halted.
name: String representing the name of the election.
random_alphanumeric: String containing the rcandom alphanumeric used
for final tiebreaks.
"""
self.ballots = ballots
self.can_eliminate_no_confidence = can_eliminate_no_confidence
self.can_random_tiebreak = can_random_tiebreak
Expand All @@ -512,18 +389,16 @@ def droop_quota(self, seats, votes):
This threshold is the minimum number of votes a candidate must receive
in order to be elected outright.

Args:
seats_vacant: Integer value of the seats vacant.
votes: Float value of the value of votes cast.
Returns: An int representing the vote quota
:param seats: Integer value of the seats vacant.
:param votes: Float value of the value of votes cast.
:return An int representing the vote quota
"""
return (float(votes) / (float(seats) + 1.0)) + 1.0

def compute_results(self):
"""Run the election using the single transferable vote algorithm.

Returns:
ElectionResults containing the election results and data.
:return ElectionResults containing the election results and data.
"""

election_rounds = list()
Expand Down Expand Up @@ -764,7 +639,9 @@ def compute_results(self):

# Sort the candidates by uid according to the random
# alphanumeric.
candidates_random_sort = sorted(candidates_to_eliminate, key=lambda candidate: [tiebreak_alphanumeric.index(c) for c in candidate.uid])
candidates_random_sort = sorted(
candidates_to_eliminate,
key=lambda candidate: [tiebreak_alphanumeric.index(c) for c in candidate.uid])
# Eliminate the first candidate in this random sort that is not
# No Confidence.
for candidate in candidates_random_sort:
Expand Down
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