Get max score

scores = [
    {'score': 17, 'user': 'a', 'level_key': 1},
    {'score': 18, 'user': 'a', 'level_key': 1},
    {'score': 16, 'user': 'a', 'level_key': 1},
    {'score': 16, 'user': 'b', 'level_key': 1},
    {'score': 17, 'user': 'b', 'level_key': 1},
    ]

import collections
data = collections.defaultdict(list)
for score in scores:
    data[score['user'],score['level_key']].append(score['score'])
output = [{'user': info[0], 'level_key': info[1], 'score': max(j)} for info,j in data.items()]
print output