STV dies with a tie

[andymckay]

Traceback (most recent call last):
  File "test.py", line 28, in <module>
    pprint(STV(counts).as_dict())
  File "/Users/andy/sandboxes/dsf/python-vote-core-20120423.0/pyvotecore/stv.py", line 30, in __init__
    super(STV, self).__init__(ballots, tie_breaker=tie_breaker, required_winners=required_winners)
  File "/Users/andy/sandboxes/dsf/python-vote-core-20120423.0/pyvotecore/abstract_classes.py", line 76, in __init__
    super(MultipleWinnerVotingSystem, self).__init__(ballots, tie_breaker)
  File "/Users/andy/sandboxes/dsf/python-vote-core-20120423.0/pyvotecore/abstract_classes.py", line 59, in __init__
    super(FixedWinnerVotingSystem, self).__init__(ballots, tie_breaker)
  File "/Users/andy/sandboxes/dsf/python-vote-core-20120423.0/pyvotecore/abstract_classes.py", line 36, in __init__
    self.calculate_results()
  File "/Users/andy/sandboxes/dsf/python-vote-core-20120423.0/pyvotecore/stv.py", line 73, in calculate_results
    if ballot["ballot"][0] in round["winners"]:
IndexError: list index out of range

I'm trying to reproduce this with a simple data set and not succeeding yet. Our dataset goes through a few rounds and would get to a point like this:

            {'loser': 'F',
             'tallies': {'C': 6.0, 'F': 3.0, 'I': 5.0, 'K': 8.0}},
            {'loser': 'I', 'tallies': {'C': 8.0, 'I': 5.0, 'K': 9.0}},
            {'loser': 'K',
             'tallies': {'C': 11.0, 'K': 11.0},
             'tied_losers': set(['C', 'K'])},

This is our current data set:

[{'ballot': ['K'], 'count': 1},
 {'ballot': ['K', 'H', 'I', 'C', 'G', 'D', 'E', 'F', 'J'], 'count': 1},
 {'ballot': ['C', 'E', 'J', 'K', 'F', 'H', 'I', 'G', 'D'], 'count': 1},
 {'ballot': ['K', 'H', 'I', 'F', 'G', 'D', 'J', 'E'], 'count': 1},
 {'ballot': ['C', 'K', 'E', 'I', 'G', 'H', 'F', 'J', 'D'], 'count': 1},
 {'ballot': ['K', 'I', 'H', 'F', 'G', 'E', 'D', 'J', 'C'], 'count': 1},
 {'ballot': ['K', 'H', 'I', 'D', 'C', 'G', 'F', 'E', 'J'], 'count': 1},
 {'ballot': ['K', 'I', 'H'], 'count': 1},
 {'ballot': ['I', 'F', 'H', 'C'], 'count': 1},
 {'ballot': ['C', 'K', 'F'], 'count': 1},
 {'ballot': ['H', 'I', 'C', 'E', 'G', 'F', 'D', 'J', 'K'], 'count': 1},
 {'ballot': ['K', 'H', 'I', 'F', 'E', 'C', 'D', 'G', 'J'], 'count': 1},
 {'ballot': ['F', 'C', 'I', 'K', 'D', 'G', 'J', 'E', 'H'], 'count': 1},
 {'ballot': ['F', 'K', 'I', 'C', 'H', 'D', 'G', 'E', 'J'], 'count': 1},
 {'ballot': ['E', 'F', 'C', 'H', 'I', 'D', 'G', 'J', 'K'], 'count': 1},
 {'ballot': ['I', 'H', 'K', 'F', 'G', 'D', 'C', 'E', 'J'], 'count': 1},
 {'ballot': ['C', 'H', 'I', 'J', 'K', 'G', 'F', 'E', 'D'], 'count': 1},
 {'ballot': ['J', 'C', 'H', 'I', 'K', 'G', 'F', 'D', 'E'], 'count': 1},
 {'ballot': ['K', 'C', 'I', 'H', 'J', 'G', 'F', 'D', 'E'], 'count': 1},
 {'ballot': ['C', 'K', 'J'], 'count': 1},
 {'ballot': ['I', 'C', 'H', 'F', 'G', 'K', 'J', 'D', 'E'], 'count': 1},
 {'ballot': ['H', 'I', 'K', 'F', 'G', 'C', 'J', 'E', 'D'], 'count': 1}]

[bradbeattie]

Thanks Andy. I'm actually in the middle of rewriting the entire library to be PyPy compatible. I'll add this ballot set to the set of tests!

[andymckay]

Out of curiosity what do you do propose to do in this case? Just declare it a tie?