Paul

Python 3 with MongoDB

A quick tutorial to demonstrate Python 3 with MongoDB

 Installing Python 3 and PyMongo

Download and install the latest version of Python 3 (version 3.3 at time of writing) from http://www.python.org/download/releases/

Make sure to select ‘Add python.exe to path’

Next we need to download the installer for Distribute for Python from http://python-distribute.org/distribute_setup.py . Now open an command prompt by opening the start menu
and typing cmd then press enter. Change to the folder where you downloaded Distribute (eg. cd c:\users\username\downloads) and run

python distribute_setup.py

This will download and install distribute to your Python 3 folder.

Now keep the command prompt open and change to the scripts folder inside the Python 3 folder (eg. cd c:\python33\scripts\) and run

easy_install pymongo

Once this completes, PyMongo is installed. We can test this by opening python in a command prompt and typing

import pymongo

If no errors occur then everything went ok and we can start using pymongo to work with MongoDB

Using PyMongo

We need to make a connection to work with a MongoDB database

from pymongo import Connection
connection=Connection() 
or 
connection=Connection('ip','port') if using a remote host

Next we need to select the database to use.

database=connection['mydatabase']

We don’t have to create databases or collections, if they don’t exists they will be created.

mycollection=database.entries

‘entries’ is a collection (similar to a table in a RDBMS) and will be created if needed.

Inserting Data in MongoDB

We store data in MongoDB using documents which are defined in Key Value pairs in PyMongo

post1={"title":"My first post","details":"This is my first entries on PyMongo"}

Then we insert the document into a collection

mycollection.insert(post1)

Now we’ll make a second document with a different set of columns.

post2={"title":"My second post","date":"05/11/2012","author":"Paul"}
mycollection.insert(post2)

We don’t have to use any of the same data names but it’s better to keep the documents some what similar in the same collection.

Retrieving one document

We use find({key:value}) to find a single document or we only want to get back the first document matching the condition.

print(mycollection.find_one({"title":"My second post"}))

This should return (ObjectId is unique to each document and assigned automatically)

{'title': 'My second post', 'date': '05/11/2012', '_id': ObjectId('509837c62fc1c02c91056697'), 'author': 'Paul'}

 Retrieving all documents

 for entry in mycollection.find():
    print(entry)

We can also filter the results like find_one()

for entry in mycollection.find("title":"My first post"):
    print(entry)

In the next tutorial, I’ll show how to update documents, delete documents and indexes

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