MongoDB and Python

MongoDB is a cross-platform, document-oriented database that works on the concept of collections and documents. MongoDB offers high speed, high availability and high scalability.

Features of MongoDB

1. It supports hierarchical data structure.
2. It supports associate arrays like Dictionaries in Python.
3. Built-in Python drivers to connect python-application with Database. Example- PyMongo
4. It is designed for Big Data.
5. Deployment of MongoDB is very easy.

MongoDB vs RDBMS

Connecting MongoDB with Python Using PyMongo

Step 1: Start MongoDB

Start MongoDB from the command prompt using the following command:

If starting with default settings:

mongod

When running directly with custom data directory:

mongod --dbpath "C:\data"

If MongoDB is installed as a Windows service:

net start MongoDB

See port number by default is set 27017 (last 2-3 lines in above image).

Step 2: Install and Import PyMongo

PyMongo is the native Python library for MongoDB.

To install PyMongo, open Command Prompt and run:

pip install pymongo

After installation, open a Python environment and import the library:

from pymongo import MongoClient

Step 3: Connect to MongoDB Server

After importing, next step is to create a MongoClient.

client = MongoClient()

Connect to the default MongoDB host and port (localhost:27017) using the following command to create a MongoClient explicitly.

client = MongoClient("mongodb://localhost:27017/")

Step 4: Access/Create a Database

To create a database or switch to an existing database use:

mydatabase = client["my_database"]

Or:

mydatabase = client.my_database

Note: Database names should not contain dashes (-). The names like my-Table will raise an error. Use underscores (_) instead.

Step 5: Access/Create a Collection

Collections are equivalent to Tables in Relational Database Management Systems (RDBMS). A collection in PyMongo is accessed similarly to how tables are accessed in RDBMS.

To access the table, table name “myTable” of the database “mydatabase”.

mycollection = mydatabase[‘myTable’]

MongoDB store the database in the form of dictionaries as shown:

record = {
title: 'MongoDB and Python',
description: 'MongoDB is no SQL database',
tags: ['mongodb', 'database', 'NoSQL'],
viewers: 104
}

‘_id’ is a 12 bytes hexadecimal number. A special key which uniquely identifies each document in a collection and automatically added when not added explicitly.

Step 6: Inserting data inside collection

Methods used:

insert_one() or insert_many()

Insert the document into a collection:

rec = mycollection.insert_one(record)

The complete code looks like this when implemented:

from pymongo import MongoClient
client=MongoClient()

client = MongoClient(“mongodb://localhost:27017/”)

mydb = client[‘my_database’]
mycollection = mydb[‘myTable’]

record = {
title: 'MongoDB and Python', 
description: 'MongoDB is no SQL database', 
tags: ['mongodb', 'database', 'NoSQL'], 
viewers: 104 
}

rec = mydb.myTable.insert(record)

Step 7: Querying the Database

Certain query functions are used to filter data in a MongoDB database. Among them, the two most commonly used are:

find(): used to retrieve multiple documents from a collection that match a given query.

for i in mycollection.find({"title": "MongoDB and Python"}):
      print(i)

count_documents(): used to count the number of documents in a collection that match a specific query.

count = mycollection.count_documents({"title": "MongoDB and Python"})
print(count)

To print all the documents/entries inside 'myTable' of database 'mydatabase':

from pymongo import MongoClient

try:
    conn = MongoClient("localhost", 27017)
    print("Connected successfully!")
except Exception as e:
    print("Could not connect to MongoDB:", e)

db = conn["mydatabase"]

collection = db["myTable"]
for record in collection.find():
    print(record)

Explanation:

• connects to the local MongoDB server on port 27017 using MongoClient.
• accesses the mydatabase database and myTable collection.
• uses find() to retrieve all documents from the collection and prints it.

Related Articles:

• MongoDB : An introduction
• MongoDB and PyMongo Installation Guide