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
- It supports hierarchical data structure.
- It supports associate arrays like Dictionaries in Python.
- Built-in Python drivers to connect python-application with Database. Example- PyMongo
- It is designed for Big Data.
- 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.
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