[FIXED] Flatten a list of dictionaries in python

Issue

I have a list of dictionaries:

data = [{"average": 2, "day": "2022-01-01", "name": "joe", "employee_id": 1},
        {"average": 3, "day": "2022-01-02", "name": "joe", "employee_id": 1},
        {"average": 9, "day": "2022-01-03", "name": "joe", "employee_id": 1},
        {"sum": 13,    "day": "2022-01-01", "name": "joe", "employee_id": 1},
        {"sum": 15,    "day": "2022-01-02", "name": "joe", "employee_id": 1},
        {"sum": 0,     "day": "2022-01-03", "name": "joe", "employee_id": 1},
        {"average": 1, "day": "2022-01-01", "name": "bob", "employee_id": 2},
        {"average": 3, "day": "2022-01-02", "name": "bob", "employee_id": 2},
        {"sum":     9, "day": "2022-01-01", "name": "bob", "employee_id": 2},
        {"sum":     8, "day": "2022-01-02", "name": "bob", "employee_id": 2}]

I want my output as:

output = [{"name": "joe", "employee_id": 1, "day": "2022-01-01", "average": 2, "sum": 13},
          {"name": "joe", "employee_id": 1, "day": "2022-01-02", "average": 3, "sum": 15},
          {"name": "joe", "employee_id": 1, "day": "2022-01-03", "average": 9, "sum": 0},
          {"name": "bob", "employee_id": 2, "day": "2022-01-01", "average": 1, "sum": 9},
          {"name": "bob", "employee_id": 2, "day": "2022-01-02", "average": 3, "sum": 8}]

The goal is that the output values are put together by day, name, and employee_id.

I've tried:

output = {}
for item in data:
    if item["day"] not in output:
        output[item["day"]] = item
    else:
        output[item["day"]].update(item)
print(list(output.values()))

This works in getting the "average" and "sum" and "date" together, but it ends up not including all of the employees and their IDs.

Any help is appreciated

Solution

Using collections.defaultdict with dict. Here, take the value of 'day' and 'name' of each dictionary as the key:

>>> from collections import defaultdict
>>> defdict = defaultdict(dict)
>>> for mp in data:
...     defdict[mp['day'], mp['name']].update(mp)
...
>>> keys = ('name', 'employee_id', 'day', 'average', 'sum')
>>> [{k: mp[k] for k in keys} for mp in defdict.values()]
[{'name': 'joe', 'employee_id': 1, 'day': '2022-01-01', 'average': 2, 'sum': 13},
 {'name': 'joe', 'employee_id': 1, 'day': '2022-01-02', 'average': 3, 'sum': 15},
 {'name': 'joe', 'employee_id': 1, 'day': '2022-01-03', 'average': 9, 'sum': 0},
 {'name': 'bob', 'employee_id': 2, 'day': '2022-01-01', 'average': 1, 'sum': 9},
 {'name': 'bob', 'employee_id': 2, 'day': '2022-01-02', 'average': 3, 'sum': 8}]

Answered By - Mechanic Pig