from flask import Flask
from flask.ext.pymongo import PyMongo
from pymongo import Connection
connection = Connection()
db = connection.test_database
collection = db.test_collection
app = Flask(__name__)
mongo = PyMongo(app)
@app.route("/")
def hello():
    return "Hello World!"
if __name__ == "__main__":
    app.run()

/usr/bin/python2.7 /home/user/djcode/mybg/mybg.py
Traceback (most recent call last):
  File "/home/user/djcode/mybg/mybg.py", line 5, in <module>
    connection = Connection()
  File "/usr/local/lib/python2.7/dist-packages/pymongo/connection.py", line 220, in __init__
    max_pool_size, document_class, tz_aware, _connect, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/pymongo/mongo_client.py", line 336, in __init__
    raise ConnectionFailure(str(e))
pymongo.errors.ConnectionFailure: could not connect to localhost:27017: [Errno 111] Connection refused
Process finished with exit code 1

$ mongo
MongoDB shell version: 2.4.4
connecting to: test

mkdir -p /data/db
chown mongodb /data/db

sudo service mongodb restart