Merging list of dictionaries

I have the following list of dictionaries:

"entities": [
        {
            "length": 6,
            "offset": 0,
            "type": "bold"
        },
        {
            "length": 6,
            "offset": 0,
            "type": "italic"
        },
        {
            "length": 4,
            "offset": 7,
            "type": "italic"
        }
    ],

I would like to know how to use this input to derive the following list of dictionaries:

"entities": [
            {
                "length": 6,
                "offset": 0,
                "type": "bold_italic"
            },
            {
                "length": 4,
                "offset": 7,
                "type": "italic"
            }
        ],

>Solution :

Group each entry by their length and offset into a dictionary, noting the seen types in a list. Then, read off the computed result back into a list, creating a new dictionary for each unique length/offset pair and joining all of the types with underscores:

from collections import defaultdict

data = [
        {
            "length": 6,
            "offset": 0,
            "type": "bold"
        },
        {
            "length": 6,
            "offset": 0,
            "type": "italic"
        },
        {
            "length": 4,
            "offset": 7,
            "type": "italic"
        }
]

entry_types = defaultdict(list)
for item in data:
    key = item['length'], item['offset']
    entry_types[key].append(item['type'])

result = []
for (length, offset), types in entry_types.items():
    result.append(dict(length=length, offset=offset, type='_'.join(types)))

print(result)

This outputs:

[{'length': 6, 'offset': 0, 'type': 'bold_italic'}, {'length': 4, 'offset': 7, 'type': 'italic'}]