python-mongodb

Contains details on how we use pymongo to connect python with mongodb

Prerequisites

Download and install Python on your machine (in this example: Windows). To confirm if your installation is right, type ‘python’ in your command line window. You should get:

Python 3.9.0 (tags/v3.9.0:9cf6752, Oct  5 2020, 15:34:40) [MSC v.1927 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

We recommend that you set up a MongoDB Atlas free tier cluster for this tutorial.

Connecting Python and MongoDB Atlas

PyMongo has a set of packages for Python MongoDB interaction. To install PyMongo, open command line and type:

python -m pip install pymongo

Tip: If you are getting “ModuleNotFoundError: No module named 'pymongo'” error, uninstall pymongo.

Use

pip uninstall pymongo 

command. Then, re-install using the installation command. For this python mongodb tutorial, we use mongodb srv URI, so let’s install dnspython:

python -m pip install dnspython

Now, we can use pymongo as a python mongodb library in our code with an import statement.

Creating a database in Python MongoDB

First, get the client using the connection string. Then, create the database from the client using the database name.

from pymongo import MongoClient
import pymongo

# Provide the mongodb atlas url to connect python to mongodb using pymongo
CONNECTION_STRING = 'mongodb+srv://m001-student:m001-mongodb-basics@sandbox.qurli.mongodb.net/myFirstDatabase'

# Create a connection using MongoClient. You can import MongoClient or use pymongo.MongoClient
from pymongo import MongoClient
client = MongoClient(CONNECTION_STRING)

# Create the database for our example (we will use the same database throughout the tutorial
return client['user_shopping_list']

dbname = get_database()

Creating a collection in Python MongoDB

To create a collection, pass the collection name to the database. Make sure to have the right indentation while copying the code to your .py file.

collection_name = dbname["user_1_items"]

Inserting documents in Python MongoDB

For inserting many documents at once, use the pymongo insert_many() method.

item_1 = {
"_id" : "U1IT00001",
"item_name" : "Blender",
"max_discount" : "10%",
"batch_number" : "RR450020FRG",
"price" : 340,
"category" : "kitchen appliance"
}

item_2 = {
"_id" : "U1IT00002",
"item_name" : "Egg",
"category" : "food",
"quantity" : 12,
"price" : 36,
"item_description" : "brown country eggs"
}
collection_name.insert_many([item_1,item_2])

Let us insert a third document without specifying the _id field. This time we add a field of data type ‘date’. To add date using pymongo, use the python dateutil package. ISODate will not work with Python, as it is a Mongo shell function. Install the package using the following command:

python -m pip install python-dateutil

Add the following to pymongo_test.py:

from dateutil import parser
expiry_date = '2021-07-13T00:00:00.000Z'
expiry = parser.parse(expiry_date)
item_3 = {
"item_name" : "Bread",
"quantity" : 2,
"ingredients" : "all-purpose flour",
"expiry_date" : expiry
}
collection_name.insert_one(item_3)

We use the insert_one() method to insert a single document. Open the command line and navigate to the folder where you have saved pymongo_test_insert.py. Execute the file using the python pymongo_test_insert.py command.

Querying in Python MongoDB

To query, we use the find() method.

dbname = get_database()

# Create a new collection
collection_name = dbname["user_1_items"]

item_details = collection_name.find()
for item in item_details:
	# This does not give a very readable output
	print(item)

Indexing in Python MongoDB

Let us create a single index on the ‘category’ field.

category_index = collection_name.create_index("category")