MongoEngine - Connecting to MongoDB Database

As mentioned earlier, you should first start MongoDB server using mongod command.

MongoEngine provides connect() function to connect to a running instance of mongodb server.

>>>from mongoengine import connect
>>>connect(mydata.db)
MongoClient(host=['localhost:27017'], document_class=dict, tz_aware=False, connect=True, read_preference=Primary(), uuidrepresentation=3, driver=DriverInfo(name='MongoEngine', version='0.29.1', platform=None))

By default, MongoDB server is running on localhost and on port 27017. To customize, you should provide the host and port arguments to connect() −

connect('mydata.db', host='192.168.1.1', port=12345)

In case the database requires authentication, its credentials such as username, password and authentication_source arguments should be provided.

connect('mydata.db', username='user1', password='***', authentication_source='admin')

MongoEngine also supports URI style connections instead of IP address.

connect('mydata.db', host='mongodb://localhost/database_name')

The connect() function has another optional parameter called replicaset. MongoDB is a distributed database. Data stored in one server is usually replicated in many server instances in order to ensure high availability. A replica set in MongoDB is a group of mongod processes on which the same data set is maintained. Replica sets are the basis for all production deployments.

connect(host='mongodb://localhost/dbname?replicaSet=rs-name')

Following replica set methods are defined as follows:

MongoEngine also allows connection with multiple databases. You need to provide unique alias name for each database. For example, following code connects Python script to two MongoDB databases.

connect(alias='db1', db='db1.db')
connect(alias='db2', db='db2.db')