Spoiler of http://stackoverflow.com/questions/22572089/python-how-to-create-dict-from-a-txt-file/22572486#22572486

gistfile1.py

from collections import defaultdict
def person_to_club(_file):
  result = defaultdict(list)
  with open(_file) as memberships:
    for line in filter(None, (l.strip() for l in memberships)):
      if ',' in line:
        key = line
      else:
        result[key].append(line)
  return result