Work out possible coalitions for the UK 2017 general election

coalition2017.py

"""2017 general election
Given the vote totals, we have a hung parliament. Work out how coalitions
might be put together and display possibilities.
"""
import itertools

# vote totals correct as of about 10.30am Friday 9th June 2017
votes= {
    'Conservative': 318, 'Sinn Fein': 7, 'DUP': 10, 
    'Sylvia Hermon': 1, 'Plaid Cymru': 4, 'Labour': 261, 'SNP': 35, 
    'Liberal Democrat': 12, 'Green Party': 1
}

abbrs = {
    'Conservative': 'CON', 'Sinn Fein': 'SF', 'DUP': 'DUP', 
    'Sylvia Hermon': 'Hermon', 'Plaid Cymru': 'PC', 'Labour': 'LAB', 'SNP': 'SNP', 
    'Liberal Democrat': 'LD', 'Green Party': 'Green'
}

items = votes.items()

combs = {}
winners = {}

# There are 650 MPs, so 326 is a majority. But Sinn Fein don't take their seats (7, as above)
# and the speaker and two deputy speakers don't really count, so a practical "if you have this
# many then you look like a viable coalition government" is 320.
WINTOTAL = 320

for L in range(0, len(items)+1):
  for subset in itertools.combinations(items, L):
    parties = [x[0] for x in subset]

    # OK, reject combinations that won't happen. First: don't display single parties in the list
    if len(parties) == 1: continue
    # There will be no Conservative + Labour coalition, obviously
    if "Conservative" in parties and "Labour" in parties: continue
    # The DUP explicitly said they don't like Labour
    if "Democratic Unionist Party" in parties and "Labour" in parties: continue
    # The LDs explicitly said they wouldn't go into coalitions with anyone
    if "Liberal Democrat" in parties: continue
    # Sinn Fein don't take their seats and will continue to not do so
    if "Sinn Fein" in parties: continue
    # No Green + CON: https://twitter.com/TheGreenParty/status/873023912430325765
    if "Conservative" in parties and "Green Party" in parties: continue

    parties.sort(key=lambda p:(votes[p],p), reverse=True)
    name = set([abbrs[x] for x in parties])
    namestr = ", ".join([abbrs[x] for x in parties])
    lnamestr = ", ".join(parties)
    if len(lnamestr) < 40: namestr = lnamestr
    total = sum([x[1] for x in subset])
    if total < 300: continue
    combs[namestr] = total
    if total >= WINTOTAL:
        winners[namestr] = name

# Throw out all supersets; that is, if CON+DUP is enough to win, then obviously CON+DUP+PC
# is too, but don't count it; things on the winning list are the minimum possible. We don't
# throw out supersets of non-winning coalitions.
binit = set()
for ns, n in winners.items():
    for checkns, checkn in winners.items():
        if n < checkn:
            binit.add(checkns)

for b in binit:
    del combs[b]

ii = list(combs.items())
ii.sort(key=lambda c: c[1], reverse=True)

banner = False

# and print the output graph.
print()
for n, v in ii:
    vc = v // 20
    bar = "█" * vc
    endbar = " " * (20 - vc)
    if v < WINTOTAL and not banner:
        print("          —————————— %s needed to look plausible? ——————————" % WINTOTAL)
        banner = True
    print (" %s%s%2d %s" % (bar, endbar, v, n))
print()