Introduction

In this article, we are going to develop an interaction between Python and MongoDB.

In another article , we set up a MongoDB Atlas account and also completed some basic exercises in Mongo DB, such as creating a database, creating a collection and inserting some documents as well. If you are interested, then please go through this article before starting.

Before beginning this, I am expecting that you should aware of the basics of Python. This article is not covering Python installation and setup

Atlas Setup

First, open the mongodb Atlas in a browser.

Select cluster from the left panel.

And press the CONNECT button.

You will see a popup with three options. We will explore each option.

Here, we will choose the “Connect to your Application” option

We will get a popup with 2 options:

DRIVERS and VERSIONS

Connection String or Full driver example

From drivers, select Python and the latest version after that. Copy the connection string only.

mongodb+srv://admin:<password>@cluster0-kbpys.mongodb.net/test?retryWrites=true&w=majority

Note

You need to replace the actual password with <password> You need to replace the actual password with

Now open any Python editor. I am using PyCharm.

Start development

First, open pycharm.

Create an open sample project.

Open a terminal in pycharm.

Now install mongodb dependencies for python from the terminal.

pip3 install pymongo[srv]

Create one sample py file, mongo_atlas_database.py

Here we are going to print all databases and also add one database.

import pymongo client = pymongo.MongoClient( "<the atlas connection string>" )

Copy the connection string from Atlas and paste it here.

import pymongo client = pymongo.MongoClient( "mongodb+srv://admin:admin123@cluster0-kbpys.mongodb.net/test?retryWrites=true&w=majority" ) for name in client.list_database_names(): print (name)

The output should look like:

Now we try to list the database and respective collections.

import pymongo client = pymongo.MongoClient( "mongodb+srv://admin:admin123@cluster0-kbpys.mongodb.net/test?retryWrites=true&w=majority" ) for database_name in client.list_database_names(): print ( "Database - " +database_name) for collection_name in client.get_database(database_name).list_collection_names(): print (collection_name)

CRUD Operations

As we know in mongodb provides us database at the top hierarchy. In the database, we store collections and inside the collections, we add documents.

Create document

First, we create a database.

import pymongo client = pymongo.MongoClient( "mongodb+srv://admin:admin123@cluster0-kbpys.mongodb.net/test?retryWrites=true&w=majority" ) collection = client.libraryDB.books booksData = [ { "id" : "01" , "language" : "Java" , "edition" : "third" , "author" : "Herbert Schildt" }, { "id" : "07" , "language" : "C++" , "edition" : "second" , "author" : "E.Balagurusamy" } ] collection.insert_many(booksData)

Using collection.insert_many(booksData) we can able add multiple documents in collection.

View document

To verify the documents are added or not, we have two options.

Option 1 - View documents in MongoDB atlas

Select cluster from the left panel.

And press the COLLECTIONS button.

Option 2

Write code in Python to retrieve records:

print ( 'Find One document' ) print (client.libraryDB.books.find_one()) print ( 'Find all documents' ) for x in client.libraryDB.books.find(): print (x) print ( 'Find documents with condition' ) for x in client.libraryDB.books.find({ "language" : "Java" }): print (x)

Update document

myquery = { "language" : "Advanced Java" } newvalues = { "$set" : { "language" : "Java" }} client.libraryDB.books.update_one(myquery, newvalues) Delete document

myquery = { "language" : "Java" } client.libraryDB.books.delete_one(myquery)

Indexing

Indexing is used to improve the performance while retrieving the documents

client.libraryDB.books.create_index([('name', 1)])

1: Ascending

-1: Descending

Index Types Single Field collection.create_index([('name', 1)])

Compound Index client.libraryDB.books.createIndex( { <field1>: <type>, <field2>: <type2>, ... } )

Aggregation

Aggregation operations process data records and also return computed results. Aggregation operations group values from multiple documents together and can perform a variety of operations on the grouped data to return a single result. So, complex computations can easily handle by aggregation.

client.libraryDB.books.aggregate([ { $match: { 'language' : 'Java' } }, { $group: { _id: "$cust_id" , total: { "$sum" : "$amount" } } } ])

Summary

We have learned some writing with simple CRUD operations, then we learned the concept of indexing and the use of aggregation. If you need more information, then please go through the below links: