適当にdictの複合体をサーチ

HOGE = {
    '1' : [
        dict( card_id = '101', card_data = dict( level = 10 ) ),
        dict( item_id = '5', item_num = 10),
        ],
    '2' : [
        dict( card_id = '102', card_data = dict( level = 10 ) ),
        dict( item_id = '5', item_num = 10),
        ],
    '3' : [
        dict( card_id = '103', card_data = dict( level = 10 ) ),
        dict( item_id = '5', item_num = 10),
        ],
    '4' : [dict( item_id = '5', item_num = 2 )],
    }

print HOGE
for a in HOGE.values():
    for b in a:
        for c in b.items():
            if 'item_num' in c:
                print c

結果

{'1': [{'card_data': {'level': 10}, 'card_id': '101'}, {'item_num': 10, 'item_id': '5'}], '3': [{'card_data': {'level': 10}, 'card_id': '103'}, {'item_num': 10, 'item_id': '5'}], '2': [{'card_data': {'level': 10}, 'card_id': '102'}, {'item_num': 10, 'item_id': '5'}], '4': [{'item_num': 2, 'item_id': '5'}]}
('item_num', 10)
('item_num', 10)
('item_num', 10)
('item_num', 2)