purcell.py

inputs = (('date1', 7, 'team1'),
          ('date1', 9, 'team2'),
          ('date2', 10, 'team3'))

date_to_data = {}

for date, score, team in inputs:
  if not date_to_data.get(date):
    date_to_data[date] = []
  date_to_data[date].append(score)
  date_to_data[date].append(team)

for date, data in date_to_data.iteritems():
  str_data = [str(d) for d in data]
  print '%s, %s' % (date, ', '.join(str_data))