Documentation Index
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FastAPI
FastAPI is a modern, high-performance Python web framework built on Python 3.6+ type hints. With over 70k+ stars on GitHub, it’s one of the most popular Python backend frameworks today.
Core Features
- High Performance: Performance comparable to Node.js and Go
- Fast Development: Improves development efficiency 200%-300%
- Auto Docs: Automatically generates interactive API documentation
- Type Checking: Pydantic-based data validation
- Async Support: Native async/await support
Quick Start
Installation
pip install fastapi
pip install "uvicorn[standard]"
Hello World
from fastapi import FastAPI
app = FastAPI()
@app.get("/")
async def root():
return {"message": "Hello World"}
@app.get("/items/{item_id}")
async def read_item(item_id: int, q: str = None):
return {"item_id": item_id, "q": q}
Running
uvicorn main:app --reload
Path & Query Parameters
from typing import Optional
@app.get("/users/{user_id}")
async def read_user(
user_id: int,
skip: int = 0,
limit: int = 10,
q: Optional[str] = None
):
return {"user_id": user_id, "skip": skip, "limit": limit, "q": q}
Request Body
from pydantic import BaseModel
class Item(BaseModel):
name: str
description: Optional[str] = None
price: float
tax: Optional[float] = None
@app.post("/items/")
async def create_item(item: Item):
return item
Response Model
class UserOut(BaseModel):
username: str
email: str
@app.post("/users/", response_model=UserOut)
async def create_user(user: User):
return user # Automatically filters sensitive fields
Dependency Injection
from fastapi import Depends
def get_db():
db = Database()
try:
yield db
finally:
db.close()
@app.get("/users/")
async def read_users(db = Depends(get_db)):
return db.query_users()
Middleware
from fastapi.middleware.cors import CORSMiddleware
app.add_middleware(
CORSMiddleware,
allow_origins=["*"],
allow_credentials=True,
allow_methods=["*"],
allow_headers=["*"],
)
Database Integration
SQLAlchemy
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
SQLALCHEMY_DATABASE_URL = "sqlite:///./sql_app.db"
engine = create_engine(SQLALCHEMY_DATABASE_URL)
SessionLocal = sessionmaker(bind=engine)
def get_db():
db = SessionLocal()
try:
yield db
finally:
db.close()
Authentication & Authorization
from fastapi.security import OAuth2PasswordBearer
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")
@app.get("/users/me")
async def read_users_me(token: str = Depends(oauth2_scheme)):
return {"token": token}
File Upload
from fastapi import File, UploadFile
@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile = File(...)):
return {"filename": file.filename}
Background Tasks
from fastapi import BackgroundTasks
def send_email(email: str):
# Send email logic
pass
@app.post("/send-notification/")
async def send_notification(
email: str,
background_tasks: BackgroundTasks
):
background_tasks.add_task(send_email, email)
return {"message": "Email will be sent"}
Resources
