Combine lists of dictionaries with specific value matches

user_11275173 0
Viewed 81

Given a_list and b_list in python, I want to merge them so that the result is c_list.

In the example below, only want to merge elements that have a matching 'A' for the 'code' key.

a_list = [{'code': 'A', 'foo_sum': 1}, {'code': 'B', 'foo_sum': 2}]
b_list = [{'code': 'A', 'bar_sum': 3}]

c_list = [{'code': 'A', 'foo_sum': 1, 'bar_sum': 3}, {'code': 'B', 'foo_sum': 2}]

I wanted to use numpy, but could not use it because it did not necessarily match the element length and the order.

And, I tried to determine this in the iterative process, but could not achieve to make it c because local variables are not available in the comprehension notation.

for a in b_list:
    if any(b["code"] == a["code"] for i, b in enumerate(b_list):
        # want to use i variable, but not dified.
        a["bar_sum"] = b_list[i]["code"]
list dictionary python
2 Answers

You can try

  1. merge the two lists
  2. sort the merged list by code key then groupby code
  3. merge the list of dictionary in group to one dictionary
from itertools import groupby
from collections import ChainMap

c_list = a_list + b_list
c_list = sorted(c_list, key=lambda d: d.get('code'))
res = [dict(ChainMap(*group)) for key, group in groupby(c_list, lambda d: d.get('code'))]

print(res)

[{'code': 'A', 'bar_sum': 3, 'foo_sum': 1}, {'code': 'B', 'foo_sum': 2}]
user_103151630

Another solution:

a_list = [{"code": "A", "foo_sum": 1}, {"code": "B", "foo_sum": 2}]
b_list = [{"code": "A", "bar_sum": 3}]


out = {}
for d in a_list + b_list:
    out[d["code"]] = {**out.get(d["code"], {}), **d}

print(list(out.values()))

Prints:

[{"code": "A", "foo_sum": 1, "bar_sum": 3}, {"code": "B", "foo_sum": 2}]
user_100359850
Related