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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()

# CREATE
@app.post("/items/")
async def create_item(item: Item):
    ''' code implementation here '''
    
# READ
@app.get("/items/{item_id}")
async def read_item(item_id: int):
    ''' code implementation here '''

# UPDATE
@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item):
    ''' code implementation here '''

# DELETE
@app.delete("/items/{item_id}")
async def delete_item(item_id: int):
    ''' code implementation here '''

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

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