count.py

# http://www.data.parliament.uk/dataset/general-election-2015

import tablib

coalition_parties = ('Lab', 'LD', 'Green')
factor = 1.0

data = tablib.Dataset()
data.csv = open('../Desktop/hocl-ge2015-results-full.csv', 'r').read()

consituencies = {}


# {'Aberavon': {}, 'Aberconwy': {}, ...}
for line in data:
    consituencies[line[2]] = {}

# {'Aberavon': {'Lab': 15416, 'UKIP': 4971, 'Con': 3742, ...}, ...}
for line in data:
    consituencies[line[2]][line[8]] = int(line[14])

# Print number of seats won by each party
seats = {}
for results in consituencies.values():
    party = max(results.items(), key=lambda x: x[1])[0]
    if party in seats:
        seats[party] += 1
    else:
        seats[party] = 1

sorted_items = sorted(seats.items(), key=lambda x: -x[1])
for party, seats in sorted_items:
    print "%8s: %3d" % (party, seats)
print '==='

# Remove individual coalition votes and add to highest in seat.
for results in consituencies.values():
    # Get the subset of results just for coalition parties.
    subset = [
        item for item in results.items()
        if item[0] in coalition_parties
    ]
    # No coalition parties ran in seat, ignore.
    if not subset:
        continue
    # Determine the highest ranked coalition party.
    party = max(subset, key=lambda x: x[1])[0]

    total = 0
    for individual in coalition_parties:
        if individual != party and individual in results:
            extra = results[individual] * factor
            results[individual] -= extra
            results[party] += extra

# Print number of seats won by each party
seats = {}
for results in consituencies.values():
    party = max(results.items(), key=lambda x: x[1])[0]
    if party in seats:
        seats[party] += 1
    else:
        seats[party] = 1

sorted_items = sorted(seats.items(), key=lambda x: -x[1])
for party, seats in sorted_items:
    print "%8s: %3d" % (party, seats)

results.txt

$ python count.py 
     Con: 330
     Lab: 232
     SNP:  56
      LD:   8
     DUP:   8
      SF:   4
    SDLP:   3
      PC:   3
     UUP:   2
    UKIP:   1
     Ind:   1
     Spk:   1
   Green:   1
===
     Con: 285
     Lab: 260
     SNP:  52
      LD:  29
     DUP:   8
      SF:   4
    SDLP:   3
      PC:   3
     UUP:   2
    UKIP:   1
     Ind:   1
     Spk:   1
   Green:   1