# Python Driver

# Connect to MongoDB using pymongo

from pymongo import MongoClient

uri = "mongodb://localhost:27017/"

client = MongoClient(uri)

db = client['test_db']
# or
# db = client.test_db

# collection = db['test_collection']
# or
collection = db.test_collection


collection.save({"hello":"world"})

print collection.find_one()

# PyMongo queries

Once you got a collection object, queries use the same syntax as in the mongo shell. Some slight differences are:

  • every key must be enclosed in brackets. For example:
    db.find({frequencies: {$exists: true}})
    
    

    becomes in pymongo (note the True in uppercase):

    db.find({"frequencies": { "$exists": True }})
    
    
  • objects such as object ids or `ISODate` are manipulated using python classes. PyMongo uses its own [`ObjectId`](http://api.mongodb.com/python/current/api/bson/objectid.html) class to deal with object ids, while dates use the standard `datetime` package. For example, if you want to query all events between 2010 and 2011, you can do:

     from datetime import datetime
    
     date_from = datetime(2010, 1, 1)
     date_to = datetime(2011, 1, 1)
     db.find({ "date": { "$gte": date_from, "$lt": date_to } }):
    
    
  • # Update all documents in a collection using PyMongo

    Let's say you need to add a field to every document in a collection.

    import pymongo
    
    client = pymongo.MongoClient('localhost', 27017)
    db = client.mydb.mycollection
    
    for doc in db.find():
       db.update(
           {'_id': doc['_id']}, 
           {'$set': {'newField': 10} }, upsert=False, multi=False)
    
    

    The find method returns a Cursor, on which you can easily iterate over using the for in syntax. Then, we call the update method, specifying the _id and that we add a field ($set). The parameters upsert and multi come from mongodb (see here for more info).

    # Syntax

    • mongodb://[username:password@]host1[:port1][,host2[:port2],...[,hostN[:portN]]][/[database][?options]]

    # Parameters

    Parameter Detail
    hostX Optional. You can specify as many hosts as necessary. You would specify multiple hosts, for example, for connections to replica sets.
    :portX Optional. The default value is :27017 if not specified.
    database Optional. The name of the database to authenticate if the connection string includes authentication credentialsIf /database is not specified and the connection string includes credentials, the driver will authenticate to the admin database.
    ?options Connection specific options