MongoDB CRUD operations in Python

MongoDB, a popular NoSQL database, is widely used in numerous applications due to its scalability and flexibility.

Python developers often interface with MongoDB using a package called pymongo. This guide will walk you through the basic CRUD (Create, Read, Update, Delete) operations in MongoDB using Python.

Prerequisites

• MongoDB installed on your system
• Python environment set up
• pymongo installed (pip install pymongo)

1. Establishing a Connection

First, you need to connect to your MongoDB instance:

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from pymongo import MongoClient

# Connect to the default host and port
client = MongoClient()

# Alternatively, specify the host and port
# client = MongoClient('localhost', 27017)

2. Database and Collection

MongoDB organizes data in databases and collections. Here's how to specify them:

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# Choose a database (it will be created if it doesn’t exist)
db = client.mydatabase

# Choose a collection (similar to a table in relational databases)
collection = db.mycollection

3. CRUD Operations

Create

To insert a document into a collection:

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doc = {"name": "John", "age": 30, "city": "New York"}
result = collection.insert_one(doc)
print(result.inserted_id)

For multiple documents:

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docs = [
    {"name": "Anna", "age": 25, "city": "London"},
    {"name": "Mike", "age": 32, "city": "San Francisco"}
]
result = collection.insert_many(docs)
print(result.inserted_ids)

Read

To retrieve one document:

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# Find one document without any criteria
result = collection.find_one()
print(result)

# Find one document with a criteria
result = collection.find_one({"name": "John"})
print(result)

To retrieve multiple documents:

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# Find all documents
results = collection.find()

# Find documents with criteria
results = collection.find({"age": {"$gt": 30}})

for r in results:
    print(r)

Update

To update one document:

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# Update the age of John
criteria = {"name": "John"}
new_values = {"$set": {"age": 31}}
collection.update_one(criteria, new_values)

To update multiple documents:

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# Increase age by 1 for all documents where age is less than 30
criteria = {"age": {"$lt": 30}}
new_values = {"$inc": {"age": 1}}
collection.update_many(criteria, new_values)

Delete

To delete one document:

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# Delete a document with name John
collection.delete_one({"name": "John"})

To delete multiple documents:

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# Delete all documents where age is greater than 30
collection.delete_many({"age": {"$gt": 30}})

4. Closing the Connection

After performing your operations, it's good practice to close the connection:

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client.close()

Conclusion

MongoDB CRUD operations in Python using pymongo are straightforward. This guide covers the basics to get you started. However, MongoDB offers more advanced features such as indexing, aggregation, and transactions, which are worth exploring as you dive deeper into MongoDB and Python development.