In this guide, you can learn how to use a connection string and MongoClient object to connect to different types of MongoDB deployments.
To connect to a MongoDB deployment on Atlas, include the following elements in your connection string:
URL of your Atlas cluster
MongoDB username
MongoDB password
Then, pass your connection string to the MongoClient constructor.
When you connect to Atlas, we recommend using the Stable API client option to avoid breaking changes when Atlas upgrades to a new version of MongoDB Server. To learn more about the Stable API feature, see the Stable API page.
The following code shows how to use PyMongo to connect to an Atlas cluster. The code also uses the server_api option to specify a Stable API version. Select the Synchronous or Asynchronous tab to see the corresponding code:
from pymongo import MongoClientfrom pymongo.server_api import ServerApiuri = "<connection string>"client = MongoClient(uri, server_api=ServerApi( version='1', strict=True, deprecation_errors=True))try: client.connect() client.admin.command({'ping': 1}) print("Pinged your deployment. You successfully connected to MongoDB!")finally: client.close()import asynciofrom pymongo import AsyncMongoClientfrom pymongo.server_api import ServerApiasync def main(): uri = "<connection string>" client = AsyncMongoClient(uri, server_api=ServerApi( version='1', strict=True, deprecation_errors=True)) try: await client.admin.command({'ping': 1}) print("Pinged your deployment. You successfully connected to MongoDB!") finally: await client.close()asyncio.run(main())To connect to a local MongoDB deployment, use localhost as the hostname. By default, the mongod process runs on port 27017, though you can customize this for your deployment.
The following code shows how to use PyMongo to connect to a local MongoDB deployment. Select the Synchronous or Asynchronous tab to see the corresponding code:
from pymongo import MongoClienturi = "mongodb://localhost:27017/"client = MongoClient(uri)from pymongo import AsyncMongoClienturi = "mongodb://localhost:27017/"client = AsyncMongoClient(uri)To connect to a replica set, specify the hostnames (or IP addresses) and port numbers of the replica-set members in your connection string.
The following code shows how to use PyMongo to connect to a replica set that contains three hosts. Select the Synchronous or Asynchronous tab to see the corresponding code:
from pymongo import MongoClientclient = MongoClient("mongodb://host1:27017,host2:27017,host3:27017")from pymongo import AsyncMongoClientclient = AsyncMongoClient("mongodb://host1:27017,host2:27017,host3:27017")If you aren't able to provide a full list of hosts in the replica set, you can specify one or more of the hosts in the replica set and instruct PyMongo to perform automatic discovery to find the others. To instruct the driver to perform automatic discovery, perform one of the following actions:
Specify the name of the replica set as the value of the replicaSet parameter.
Specify false as the value of the directConnection parameter.
Specify more than one host in the replica set.
In the following example, the driver uses a sample connection URI to connect to the MongoDB replica set sampleRS, which is running on port 27017 of three different hosts, including host1. Select the Synchronous or Asynchronous tab to see the corresponding code:
from pymongo import MongoClienturi = "mongodb://host1:27017/?replicaSet=sampleRS"client = MongoClient(uri)from pymongo import AsyncMongoClienturi = "mongodb://host1:27017/?replicaSet=sampleRS"client = AsyncMongoClient(uri)When a replica set runs in Docker, it might expose only one MongoDB endpoint. In this case, the replica set is not discoverable. Specifying directConnection=false in your connection URI, or leaving this option unset, can prevent your application from connecting to it.
In a test or development environment, you can connect to the replica set by specifying directConnection=true. In a production environment, we recommend configuring the cluster to make each MongoDB instance accessible outside of the Docker virtual network.
PyMongo evenly load balances operations across deployments that are reachable within the client's localThresholdMS value. To learn more about how PyMongo load balances operations across multiple MongoDB deployments, see the Customize Server Selection guide.
The MongoClient constructor is non-blocking. When you connect to a replica set, the constructor returns immediately while the client uses background threads to connect to the replica set.
If you construct a MongoClient and immediately print the string representation of its nodes attribute, the list might be empty while the client connects to the replica-set members.
To initialize a replica set, you must connect directly to a single member. To do so, set the directConnection connection option to True. You can do this in two ways: by passing an argument to the MongoClient constructor or through a parameter in your connection string.
from pymongo import MongoClientclient = MongoClient("mongodb://<hostname>:<port>", directConnection=True)from pymongo import MongoClienturi = ("mongodb://<hostname>:<port>/?" "directConnection=true")client = MongoClient(uri)from pymongo import AsyncMongoClientclient = AsyncMongoClient("mongodb://<hostname>:<port>", directConnection=True)from pymongo import AsyncMongoClienturi = ("mongodb://<hostname>:<port>/?" "directConnection=true")client = AsyncMongoClient(uri)To use DNS service discovery to look up the DNS SRV record of the service you're connecting to, specify the SRV connection format in your connection string. Additionally, if you enable the SRV connection format, PyMongo automatically re-scans for new hosts without having to change the client configuration.
The following code shows a connection string that uses the SRV connection format:
uri = "mongodb+srv://<hostname>/"To learn more about the SRV connection format, see the SRV Connection Format entry in the MongoDB Server manual.
If you try to connect to MongoDB Server v3.6 or earlier, PyMongo might raise the following error:
pymongo.errors.ConfigurationError: Server at localhost:27017 reports wire version 6, but this version of PyMongo requires at least 7 (MongoDB 4.0).This occurs when the driver version is too new for the server it's connecting to. To resolve this issue, you can do one of the following:
Upgrade your MongoDB deployment to v4.0 or later.
Downgrade to PyMongo 4.10 or earlier, which supports MongoDB Server v3.6 and later.
Downgrade to PyMongo v3.x, which supports MongoDB Server v2.6 and later.
An AutoReconnect exception indicates that a failover has occurred. This means that PyMongo has lost its connection to the original primary member of the replica set, and its last operation might have failed.
When this error occurs, PyMongo automatically tries to find the new primary member for subsequent operations. To handle the error, your application must take one of the following actions:
Retry the operation that might have failed
Continue running, with the understanding that the operation might have failed
PyMongo raises an AutoReconnect error on all operations until the replica set elects a new primary member.
If you try to connect to a MongoDB replica set over an SSH tunnel, you receive the following error:
File "/Library/Python/2.7/site-packages/pymongo/collection.py", line 1560, in count return self._count(cmd, collation, session) File "/Library/Python/2.7/site-packages/pymongo/collection.py", line 1504, in _count with self._socket_for_reads() as (connection, slave_ok): File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/contextlib.py", line 17, in __enter__ return self.gen.next() File "/Library/Python/2.7/site-packages/pymongo/mongo_client.py", line 982, in _socket_for_reads server = topology.select_server(read_preference) File "/Library/Python/2.7/site-packages/pymongo/topology.py", line 224, in select_server address)) File "/Library/Python/2.7/site-packages/pymongo/topology.py", line 183, in select_servers selector, server_timeout, address) File "/Library/Python/2.7/site-packages/pymongo/topology.py", line 199, in _select_servers_loop self._error_message(selector))pymongo.errors.ServerSelectionTimeoutError: localhost:27017: timed outThis occurs because PyMongo discovers replica set members by using the response from the isMaster command, which contains the addresses and ports of the other replica set members. However, you can't access these addresses and ports through the SSH tunnel.
Instead, you can connect directly to a single MongoDB node by using the directConnection=True option with SSH tunneling.
To learn more about creating a MongoClient object in PyMongo, see the following API documentation:
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