Fold the values ​of two dictionaries if the definite key matches

I have a list of lists that contain dictionaries.

users = [[{'USERID': 302154, 'SALARY': 130.645, 'EXPERIENCE': 9},
          {'USERID': 506005, 'SALARY': 140.137, 'EXPERIENCE': 3}],
         [{'USERID': 302154, 'SALARY': 121.0, 'EXPERIENCE': 9},
          {'USERID': 506005, 'SALARY': 57.987, 'EXPERIENCE': 3}]
         ]

I want to get one dictionary for each user and summarize the "Salary" by "UserID":

result = [{'USERID': 302154, 'SALARY': 251.645, 'EXPERIENCE': 9},
          {'USERID': 506005, 'SALARY': 198.124, 'EXPERIENCE': 3}]

How do I implement this?

>Solution :

You can use itertools.chain to flatten the list and simply iterate and add the SALARY using a dictionary as intermediate container:

from itertools import chain

out = {}
for d in chain.from_iterable(users):
    if d['USERID'] in out:
        out[d['USERID']]['SALARY'] += d['SALARY']
    else:
        out[d['USERID']] = d.copy() # making a copy to avoid modifying original

out = list(out.values())

output:

[{'USERID': 302154, 'SALARY': 251.645, 'EXPERIENCE': 9},
 {'USERID': 506005, 'SALARY': 198.124, 'EXPERIENCE': 3}]