Last updated: Sep 26, 2023

Create REST API to perform CRUD Operations using FastAPI and MongoDB

In this tutorial, you'll learn how to create REST API to perform CRUD operations using FastAPI with MongoDB.

Follow the steps below to complete this tutorial:

1. Start by creating a new project folder:

mkdir sample_fastapi_mongodb_app

2. Navigate to your newly created project folder:

cd sample_fastapi_mongodb_app

3. Create a virtual environment inside the project root directory using the following command:
Windows:

py -m venv env

Unix/macOs:

python3 -m venv env

4. Activate the virtual environment using the command:
Windows:

.\env\Scripts\activate

Unix/macOs:

source env/bin/activate

5. Install FastAPI:

pip install fastapi

6. Install uvicorn:

pip install uvicorn

7. Install pydantic to validate email:

pip install pydantic[email]

8. Install motor. It is a coroutine-based API for non-blocking access to MongoDB:

pip install motor

9. Create a directory structure for your FastAPI project. A common structure should look like this:

├── sample_fastapi_mongodb_app
│   │── env
│   │── db
│   │    └── database.py
│   │
│   ├── endpoints
│   │     └── product.py
│   │     └── user.py
│   │
│   ├── models
│   │     └── product.py
│   │     └── PyObjectId.py
│   │
│   ├── routes
│   │     └── api.py
│   │
│   ├── __init__.py
│   ├── main.py

10. Create a model file named product.py in the src/models directory:

from pydantic import BaseModel, EmailStr, Field
from typing import Optional
import datetime
from models.PyObjectId import PyObjectId

class ProductModel(BaseModel):
    name: str = Field(
        None, title="Product Name", max_length=500
    )
    price: float = Field(..., gt=0,
                         description="The price must be greater than zero")
    created_by: EmailStr = Field(
        None, title="Creater Email"
    )

    def as_dict(self):
        return {"name": self.name,
                "price": self.price,
                "created_by": self.created_by,
                "created_at": datetime.datetime.now()}


class ProductUpdateModel(BaseModel):
    id: PyObjectId = Field(default_factory=PyObjectId, alias="_id")
    name: str = Field(
        None, title="Product Name", max_length=500
    )
    price: float = Field(..., gt=0,
                         description="The price must be greater than zero")
    updated_by: Optional[EmailStr] = Field(
        None, title="Updater Email"
    )

    def as_dict(self):
        return {"id": self.id,
                "name": self.name,
                "price": self.price,
                "updated_at": datetime.datetime.now(),
                "updated_by": self.updated_by}


def ResponseModel(data, code, message, error):
    return {
        "data": [data],
        "code": code,
        "message": message,
        "error": error
    }

11. Create a file named PyObjectId.py model file in the src/models directory:

from pydantic import BaseModel, Field as PydanticField
from bson import ObjectId

class PyObjectId(ObjectId):

    @classmethod
    def __get_validators__(cls):

        yield cls.validate

    @classmethod
    def validate(cls, v):

        if not ObjectId.is_valid(v):

            raise ValueError("Invalid objectid")

        return ObjectId(v)

    @classmethod
    def __modify_schema__(cls, field_schema):

        field_schema.update(type="string")

12. Create database.py file in the db directory:

# driver for mongodb
import motor.motor_asyncio
from models.PyObjectId import PyObjectId

db_host = "localhost"
db_port = "27017"
db_username = "your-username"
db_password = "your-password"
mongodb_string = "mongodb://{db_username}:{db_password}@{db_host}:{db_port}"
db_name = "test_database"


class Database():
    def __init__(self) -> None:
        self.connected = False
        self.mongodb_client = None

    async def db_connection(self):
        if self.connected == False:
            self.client = motor.motor_asyncio.AsyncIOMotorClient(mongodb_string)
            self.connected = True
        db = self.client[db_name]
        return db


database = Database()

# Add a new product into the database
async def add_product(product_data: dict):
    db = await database.db_connection()
    product = await db.product.insert_one(product_data)
    new_product = await db.product.find_one({"_id": product.inserted_id})
    return to_product(new_product)


# Retrieve a product by id
async def read_product(id: str):
    db = await database.db_connection()
    product = await db.product.find_one({"_id": PyObjectId(id)})
    if product:
        return to_product(product)
    return None


# Update a product by id
async def update_product(id: str, product_data: dict):
    if len(product_data) < 1:
        return False
    db = await database.db_connection()
    product = await db.product.find_one({"_id": PyObjectId(id)})
    if product:
        product["name"] = product_data.get("name")
        product["price"] = product_data.get("price")
        product["updated_by"] = product_data.get("updated_by")
        updated_product = await db.product.update_one({"_id": PyObjectId(id)}, {"$set": product})
        return updated_product.acknowledged
    return False

# Delete a product from the database


async def delete_product(id: str):
    db = await database.db_connection()
    product = await db.product.find_one({"_id": PyObjectId(id)})
    if product:
        await db.product.delete_one({"_id": PyObjectId(id)})
        return True
    else:
        return False


def to_product(item) -> dict:
    return {
        "id": str(item.get("_id")),
        "name": item.get("name"),
        "price": item.get("price"),
        "created_at": item.get("created_at"),
        "created_by": item.get("created_by"),
        "updated_at": item.get("updated_at"),
        "updated_by": item.get("updated_by")
    }

def to_product_list(items) -> list:
    return [to_product(item) for item in items]

13. Create a file named product_service.py in the src/endpoints directory:

from fastapi import APIRouter
from models.product import ProductModel, ProductUpdateModel, ResponseModel
from db.database import add_product, read_product, read_products, update_product, delete_product

# APIRouter creates path operations for product module
router = APIRouter(
    prefix="/products",
    tags=["Product"],
    responses={404: {"description": "Not found"}},
)


@router.post("/add", response_description="Product data added into the database")
async def add_product_data(product: ProductModel):
    product = product.as_dict()
    new_product = await add_product(product)
    return ResponseModel(new_product, 200, "Product added successfully.", False)


@router.put("/update")
async def update_product_data(product: ProductUpdateModel):
    product = product.as_dict()
    updated_product = await update_product(product.get("id"), product)
    return ResponseModel(updated_product, 200, "Product updated successfully.", False)


@router.delete("/{product_id}/delete")
async def delete_product_data(product_id: str):
    deleted_result = await delete_product(product_id)
    return ResponseModel(deleted_result, 200, "Product deleted successfully.", False)


@router.get("/{product_id}")
async def read_product_data(product_id: str):
    product = await read_product(product_id)
    return ResponseModel(product, 200, "Product retrieved successfully.", False)

14. Create user_service.py file for user API endpoints in the src/endpoints directory. We are not saving user data to database in this example:

from fastapi import APIRouter

# APIRouter creates path operations for product module
router = APIRouter(
    prefix="/users",
    tags=["User"],
    responses={404: {"description": "Not found"}},
)

@router.get("/")
async def read_user_data():
    return {"name": "John", "email": "john@example.com"}

15. Create api.py file in the routes directory to handle API routing:

from fastapi import APIRouter
from endpoints import product_service, user_service

router = APIRouter()
router.include_router(product_service.router)
router.include_router(user_service.router)

16. Create a main file named main.py in the project's root directory:

import uvicorn
from fastapi.middleware.cors import CORSMiddleware
from fastapi import FastAPI
from routes.api import router as api_router

app = FastAPI()

origins = ["http://localhost:8000"]

app.add_middleware(
    CORSMiddleware,
    allow_origins=origins,
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

app.include_router(api_router)

if __name__ == '__main__':
    uvicorn.run("main:app", host='127.0.0.1', port=8000, log_level="info", reload=True)
    print("running")

17. Run the application:

python main.py

To test your APIs, open http://127.0.0.1:8005/docs in your web browser. You will see a list of APIs ready for testing