Creating First REST API with FastAPI

Building a REST API in FastAPI involves decorating Python functions to handle specific HTTP methods. Using the @app decorator, you can define routes and manage requests with minimal boilerplate:

@app.get: Retrieve data
@app.post: Create data
@app.put / @app.patch: Update data
@app.delete: Remove data

Below is an example of a basic get route that returns a "Hello, FastAPI" message:

Python

from fastapi import FastAPI

# creating app
app = FastAPI()

# defining api endpoint
@app.get("/")
def first_example():
    return {"message": "Hello, FastAPI!"}

Now, start the server using command:

uvicorn main:app --reload

Open the browser and open http://localhost:8000/docs or http://127.0.0.1:8000/docs . You will be able to see the Swagger UI Home page as below:

Now try to Execute the API, you will get the success status with 200 code. The Response will be as shown below:

Screenshot-2026-03-24-164045 — Response after successfull execution

CRUD Operations

Below is an example demonstrating CRUD operations using FastAPI:

Python

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

# Define Item model
class Item(BaseModel):
    name: str
    price: float

# Temporary in-memory storage
items = {}

# CREATE
@app.post("/items/")
async def create_item(item: Item):
    item_id = len(items) + 1
    items[item_id] = item
    return {"id": item_id, "item": item}

# READ
@app.get("/items/{item_id}")
async def read_item(item_id: int):
    return items.get(item_id, {"error": "Item not found"})

# UPDATE
@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item):
    if item_id in items:
        items[item_id] = item
        return {"message": "Item updated", "item": item}
    return {"error": "Item not found"}

# DELETE
@app.delete("/items/{item_id}")
async def delete_item(item_id: int):
    if item_id in items:
        deleted_item = items.pop(item_id)
        return {"message": "Item deleted", "item": deleted_item}
    return {"error": "Item not found"}

Explanation:

app = FastAPI(): creates an app instance.
@app.post() defines the endpoint to create a new item.
@app.get() defines the endpoint to retrieve an item by ID.
@app.put() defines the endpoint to update an existing item.
@app.delete() defines the endpoint to delete an item.

For more details on CRUD operations, refer to the: FastAPI | CRUD Operations.

Creating First REST API with FastAPI

CRUD Operations

Explore