from pymongo.objectid import ObjectId ImportError: No module named objectid

问题

I made an python code that fetch tweets from Mongo collection called Tweets. I wan't to fetch only the object text and add an additional object called Sentiment.

When i loop through the Tweets and parse the json object to a string i get the error :

from pymongo.objectid import ObjectId ImportError: No module named objectid

Therefor i use the following code

import pymongo
import nltk
import json
from json import JSONEncoder
from pymongo import MongoClient
from pymongo.objectid import ObjectId

#JSON Encoder
class MongoEncoder(JSONEncoder):
    def default(self, obj, **kwargs):
        if isinstance(obj, ObjectId):
            return str(obj)
        else:            
            return JSONEncoder.default(obj, **kwargs)

#Mongo Settings
client = MongoClient()
db = client.Sentiment
Tweets = db.Tweet
TweetTraining = db.TweetTraining

#GET TEXT_TAG FROM TWEET
for tweet in Tweets.find({"lang":"nl"},{"text"}):
  print json.dumps(tweet, cls=MongoEncoder)

I hope that you can help me out. Many thanks

Erik