Substituting Variables Value in Mongodb statement - python-3.x

Question

My main intention is to dynamically change the Employees collection while using pymongo, and i was able to do it for insert commands, I am facing problems with the find command, no matter what i do exec() always returns None. but if i copy the string and run it value gets assigned to the variable.
can someone throw some light on why the exec is unable to return a resultset or assign a the resultset to a variable?
db.Employees.update_one(
{"id": criteria},
{
"$set": {
"name":name,
"age":age,
"country":country
}
}
)
from pymongo import MongoClient
import ast
client = MongoClient('localhost:27017')
db = client.TextClassifier
insert works
def mongo_insert_one(COLLECTION_NAME, JSON):
QUERY = """db.%(COLLECTION_NAME)s.insert_one( %(JSON)s )""" % locals();
exec(QUERY)
def mongo_retrive(COLLECTION_NAME, JSON):
resultset = None
query = """resultset = db.%(COLLECTION_NAME)s.find( %(JSON)s )""" % locals();
return resultset
print(mongo_retrive('hungry_intent', "{'Intent':'Hungry'}"))
neither this would work
resultset = exec(""" db.%(COLLECTION_NAME)s.find( %(JSON)s )""" % locals();)
this would not work for an entirely different reason,it says If you meant to call the 'locals' method on a 'Database' object it is failing because no such method exists.
resultset = db.locals()[COLLECTION_NAME].find()

Answer 1

PyMongo Database objects support bracket notation to access a named collection, and PyMongo's included bson module provides a much better JSON decoder than "eval":
from bson import json_util
COLLECTION_NAME = 'hungry_intent'
JSON = "{'Intent':'Hungry'}"
print(list(db[COLLECTION_NAME].find(json_util.loads(JSON))))
This will be faster and more reliable than your "eval" code, and also prevents the injection attack that your "eval" code is vulnerable to.
If you can avoid using JSON at all it could be preferable:
COLLECTION_NAME = 'hungry_intent'
QUERY = {'Intent':'Hungry'}
print(list(db[COLLECTION_NAME].find(QUERY)))