Unique list of dicts based on keys

Question

I have a list of dics:

     data = {}
     data['key'] = pointer_key
     data['timestamp'] = timestamp
     data['action'] = action
     data['type'] = type
     data['id'] = id

     list = [data1, data2, data3, ... ]

How can I ensure that for each data item in the list, only one such element exists for each "key"? If there are two keys as seen below, the most recent timestamp would win:

    list = [{'key':1,'timestamp':1234567890,'action':'like','type':'photo',id:245},
            {'key':2,'timestamp':2345678901,'action':'like','type':'photo',id:252},
            {'key':1,'timestamp':3456789012,'action':'like','type':'photo',id:212}]

    unique(list)

    list = [{'key':2,'timestamp':2345678901,'action':'like','type':'photo',id:252},
            {'key':1,'timestamp':3456789012,'action':'like','type':'photo',id:212}]

Thanks.

Answer 1

Here's my solution:

def uniq(list_dicts):
    return [dict(p) for p in set(tuple(i.items()) 
        for i in list_dicts)]

hope it will help somebody.

Answer 2

I needed this, but didn't like any of the answers here. So I made this simple and performant version.

def list_of_seq_unique_by_key(seq, key):
    seen = set()
    seen_add = seen.add
    return [x for x in seq if x[key] not in seen and not seen_add(x[key])]

# Usage
# If you want most recent timestamp to win, just sort by timestamp first
list = sorted(list, key=lambda k: k['timestamp'], reverse=True)
# Remove everything with a duplicate value for key 'key'
list = list_of_seq_unique_by_key(list, 'key')