pymongo example

pymongo_example_with_db_ref.py

import pymongo
from pymongo import Connection
from pymongo.dbref import DBRef
from pymongo.database import Database

# connect
connection = Connection()
db = Database(connection, "things")

# clean up
db.owners.remove()
db.tasks.remove()

# owners and tasks
db.owners.insert({"name":"Jim"})
db.tasks.insert([
    {"name": "read"},
    {"name": "sleep"}
    ])

# update jim with tasks: reading and sleeping
reading_task = db.tasks.find_one({"name": "read"})
sleeping_task = db.tasks.find_one({"name": "sleep"})

jim_update = db.owners.find_one({"name": "Jim"})
jim_update["tasks"] = [
    DBRef(collection = "tasks", id = reading_task["_id"]),
    DBRef(collection = "tasks", id = sleeping_task["_id"])
    ]

db.owners.save(jim_update)

# get jim fresh again and display his tasks
fresh_jim = db.owners.find_one({"name":"Jim"})
print "Jim's tasks are:"
for task in fresh_jim["tasks"]:
    print db.dereference(task)["name"]

Also there is

from bson import DBRef

Is it different from

from.dbref import DBRef

What if you remove of the referred documents? What happens then?

It seems that dbref can be imported from pymongo.database too.