Building a FastAPI REST API with MongoDB using Python: CRUD Operations, Swagger, and PyMongo

In this tutorial, we will learn how to create a REST API using FastAPI and MongoDB in Python. We will implement CRUD operations (Create, Read, Update, Delete) on a collection in MongoDB using PyMongo as our database driver. We will also use Swagger for API documentation.

Step 1: Setting up the Environment
First, we need to install the necessary libraries. You can do this using pip:

pip install fastapi uvicorn pymongo

Step 2: Create a new Python file, for example ‘main.py’, and import the required libraries:

from fastapi import FastAPI
from fastapi.responses import JSONResponse
from pymongo import MongoClient
from bson import ObjectId

Step 3: Connect to MongoDB
Next, establish a connection to your MongoDB database. Replace ‘mongodb://localhost:27017’ with your MongoDB URI:

client = MongoClient('mongodb://localhost:27017')
db = client['fastapi_mongodb']
collection = db['items']

Step 4: Create a FastAPI instance

app = FastAPI()

Step 5: Implement CRUD Operations
Now, let’s implement the CRUD operations. We will define endpoints for creating, reading, updating, and deleting items in our MongoDB collection.

# Create an item
@app.post('/items/')
async def create_item(item: dict):
    result = collection.insert_one(item)
    return JSONResponse(content={'id': str(result.inserted_id)}, status_code=201)

# Read an item
@app.get('/items/{item_id}')
async def read_item(item_id: str):
    item = collection.find_one({'_id': ObjectId(item_id)})
    if item:
        return JSONResponse(content=item, status_code=200)
    else:
        return JSONResponse(content={'message': 'Item not found'}, status_code=404)

# Update an item
@app.put('/items/{item_id}')
async def update_item(item_id: str, item: dict):
    result = collection.update_one({'_id': ObjectId(item_id)}, {'$set': item})
    if result.modified_count == 1:
        return JSONResponse(content={'message': 'Item updated successfully'}, status_code=200)
    else:
        return JSONResponse(content={'message': 'Item not found'}, status_code=404)

# Delete an item
@app.delete('/items/{item_id}')
async def delete_item(item_id: str):
    result = collection.delete_one({'_id': ObjectId(item_id)})
    if result.deleted_count == 1:
        return JSONResponse(content={'message': 'Item deleted successfully'}, status_code=200)
    else:
        return JSONResponse(content={'message': 'Item not found'}, status_code=404)

Step 6: Run the FastAPI Application
Finally, we can start the FastAPI application using Uvicorn:

uvicorn main:app --reload

Now, you can access the API at http://localhost:8000/docs to test the CRUD operations using Swagger.

That’s it! You have successfully created a FastAPI REST API with MongoDB and implemented CRUD operations. You can now build more complex APIs by adding authentication, validation, and other features to your API.