URI Connection String:

mongodb://<NETID>:<PASSWORD>@cluster0-shard-00-00-ppp7l.mongodb.net:27017,cluster0-shard-00-01-ppp7l.mongodb.net:27017,cluster0-shard-00-02-ppp7l.mongodb.net:27017/<DATABASE>?ssl=true\&replicaSet=Cluster0-shard-0\&authSource=admin

Replace and with the userid and password, and with the name of the database to which you wish to connect.

Python connection example

client = pymongo.MongoClient("mongodb://<NETID>:<PASSWORD>@cluster0-shard-00-00-ppp7l.mongodb.net:27017,cluster0-shard-00-01-ppp7l.mongodb.net:27017,cluster0-shard-00-02-ppp7l.mongodb.net:27017/<DATABASE>?ssl=true&replicaSet=Cluster0-shard-0&authSource=admin"

Use Python 2.7.9+ and use a Python driver version that supports MongoDB 3.4. For complete documentation on compatibility between the Python driver and MongoDB, see the MongoDB compatibility matrix.