group by

app.py

from base64 import b64encode
from json import dumps, loads, JSONEncoder
import pickle


class AllTypeJSONEncoder(JSONEncoder):
    def default(self, obj):
        if isinstance(obj, (list, dict, str, int, float, bool, type(None))):
            return super().default(obj)
        elif isinstance(obj, (set, )):
            return list(obj)
        return {'_python_object': b64encode(pickle.dumps(obj)).decode('utf-8')}


input_json = loads("""[ {
  "shop" : "Яндекс.Еда",
  "product" : "Манты"
}, {
  "shop" : "Яндекс.Еда",
  "product" : "Смузи"
}, {
  "shop" : "Яндекс.Еда",
  "product" : "Сырные палочки"
}, {
  "shop" : "Яндекс.Еда",
  "product" : "Шашлык"
}, {
  "shop" : "Яндекс.Музей",
  "product" : "Футболка протирашка"
}, {
  "shop" : "Яндекс.Маркет",
  "product" : "Электробритва"
}, {
  "shop" : "Яндекс.Еда",
  "product" : "Детское пюре"
}, {
  "shop" : "Яндекс.Еда",
  "product" : "Роллы"
}, {
  "shop" : "Яндекс.Маркет",
  "product" : "Ноутбук"
},  {
  "shop" : "Яндекс.Музей",
  "product" : "Фонарь Яндекс"
}, {
  "shop" : "Яндекс.Маркет",
  "product" : "Телевизор"
}, {
  "shop" : "Яндекс.Маркет",
  "product" : "Планшет"
}, {
  "shop" : "Яндекс.Еда",
  "product" : "Тирамису"
} ]""")

group_by_dict = {}

for row in input_json:
    shop = row['shop']
    product = row['product']

    if shop not in group_by_dict:
        # set - это как list, но хранит только уникальные значения
        group_by_dict[shop] = set()
    group_by_dict[shop].add(product)

print(dumps(group_by_dict, ensure_ascii=False, cls=AllTypeJSONEncoder))