import json

with open('user_review.json') as json_data:
    d = json.load(json_data)

mongo_biguser =[]

for user in d.keys():
      if len(d[user]) > 100:
        mongo_biguser.append(user)

users= {"user_ids": mongo_biguser }

@@ -28,16 +28,27 @@
 r_review
+_dictionary
 .json') 

Update users_many_reviews.py