How can you create a REST API with FastAPI in Python?

Question

ICSM Computer · Answer

Creating a 
REST API with FastAPI in Python is simple, fast, and production-ready. Below is a clean step-by-step guide.
Step 1 — Install FastAPI and Uvicorn
pip install fastapi uvicorn
Step 2 — Create an API file
Create a file named main.py:
from fastapi import FastAPI
app = FastAPI()
@app.get("/")
def read_root():
    return {"message": "Welcome to FastAPI!"}
@app.get("/hello/{name}")
def say_hello(name: str):
    return {"message": f"Hello, {name}"}
Step 3 — Run the API server
uvicorn main:app --reload
main → filename (main.py)app → FastAPI instance--reload → auto-reload on code changes (useful during development)
Example CRUD REST API
Below is a complete example for managing items in memory.
from fastapi import FastAPI
from pydantic import BaseModel
app = FastAPI()
class Item(BaseModel):
    name: str
    price: float
    in_stock: bool = True
items = {}
@app.post("/items/{item_id}")
def create_item(item_id: int, item: Item):
    items[item_id] = item
    return {"message": "Item created", "item": item}
@app.get("/items/{item_id}")
def get_item(item_id: int):
    return items.get(item_id, {"error": "Item not found"})
@app.put("/items/{item_id}")
def update_item(item_id: int, item: Item):
    items[item_id] = item
    return {"message": "Item updated", "item": item}
@app.delete("/items/{item_id}")
def delete_item(item_id: int):
    items.pop(item_id, None)
    return {"message": "Item deleted"}
Test the API
After running uvicorn, open your browser:
http://127.0.0.1:8000/docs → FastAPI’s Swagger UIhttp://127.0.0.1:8000/redoc → Alternative documentation view
FastAPI auto-generates documentation using OpenAPI — no extra code needed.
Adding CORS (optional — for frontend apps)
from fastapi.middleware.cors import CORSMiddleware
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],  # list specific domains in production
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)
With Database Example (SQLAlchemy)
Install DB dependencies first:
pip install sqlalchemy
Sample setup:
from fastapi import FastAPI, Depends
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
DATABASE_URL = "sqlite:///./test.db"
engine = create_engine(DATABASE_URL)
SessionLocal = sessionmaker(bind=engine)
app = FastAPI()
def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()
This allows injecting DB sessions into your routes.
Why FastAPI?
Feature
Benefit
Very Fast
Built on ASGI + Starlette
Auto Docs
Swagger and ReDoc
Pydantic Models
Validation + Serialization
Async Ready
Supports async/await
Production Friendly
Works well with Docker, Gunicorn, Kubernetes

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How can you create a REST API with FastAPI in Python?

Anubhav Kumar

Can you answer this question?

1 Answers

Step 1 — Install FastAPI & Uvicorn

Step 2 — Create an API file

Step 3 — Run the API server

Example CRUD REST API

Test the API

Adding CORS (optional — for frontend apps)

With Database Example (SQLAlchemy)

Why FastAPI?

Liked By

Feature	Benefit
Very Fast	Built on ASGI + Starlette
Auto Docs	Swagger & ReDoc
Pydantic Models	Validation + Serialization
Async Ready	Supports `async`/`await`
Production Friendly	Works well with Docker, Gunicorn, Kubernetes