Filter a dict of dict

Question

I new in Python and I am not sure it is a good idea to use dict of dict but here is my question. I have a dict of dict and I want to filter by the key of the inside dict:

Answer 1

Try this:

>>> { k: v['id1'] for k,v in a.items() if 'id1' in v }
{'key3': [4, 5, 6], 'key1': [0, 1, 2]}

For Python 2.x you might prefer to use iteritems() instead of items() and you'll still need a pretty recent python (2.7 I think) for a dictionary comprehension: for older pythons use:

dict((k, v['id1']) for k,v in a.iteritems() if 'id1' in v )

If you want to extract multiple values then I think you are best to just write the loops out in full:

def query(data, wanted):
    result = {}
    for k, v in data.items():
        v2 = { k2:v[k2] for k2 in wanted if k2 in v }
        if v2:
            result[k] = v2
    return result

giving:

>>> query(a, ('id1', 'id2'))
{'key3': {'id1': [4, 5, 6]}, 'key1': {'id2': [0, 1, 2], 'id1': [0, 1, 2]}}