Cara Membuat API dengan FastAPI Python

FastAPI adalah framework Python modern untuk membuat API dengan performa tinggi. Mari pelajari dari dasar.

Apa itu FastAPI?

Keunggulan FastAPI

- Sangat cepat (setara Node.js/Go)
- Auto-generate API documentation
- Type hints dan validation
- Async support
- Easy to learn
- Production ready

Setup Project

Install FastAPI

# Buat virtual environment
python -m venv venv
source venv/bin/activate  # Linux/Mac
# venv\Scripts\activate  # Windows

# Install FastAPI dan Uvicorn
pip install fastapi uvicorn[standard]

# Optional dependencies
pip install python-multipart  # form data
pip install python-jose[cryptography]  # JWT
pip install passlib[bcrypt]  # password hashing
pip install sqlalchemy  # database ORM

Project Structure

project/
├── app/
│   ├── __init__.py
│   ├── main.py
│   ├── config.py
│   ├── models/
│   │   └── __init__.py
│   ├── schemas/
│   │   └── __init__.py
│   ├── routers/
│   │   └── __init__.py
│   └── database.py
├── requirements.txt
└── .env

Basic API

Hello World

# main.py
from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
    return {"message": "Hello World"}

@app.get("/items/{item_id}")
def read_item(item_id: int, q: str = None):
    return {"item_id": item_id, "q": q}

Run Server

# Development
uvicorn main:app --reload

# Production
uvicorn main:app --host 0.0.0.0 --port 8000

# Access:
# http://localhost:8000
# http://localhost:8000/docs (Swagger UI)
# http://localhost:8000/redoc (ReDoc)

Path Parameters

Basic Path Parameters

@app.get("/users/{user_id}")
def get_user(user_id: int):
    return {"user_id": user_id}

@app.get("/files/{file_path:path}")
def get_file(file_path: str):
    return {"file_path": file_path}

Enum Path Parameters

from enum import Enum

class ModelName(str, Enum):
    alexnet = "alexnet"
    resnet = "resnet"
    lenet = "lenet"

@app.get("/models/{model_name}")
def get_model(model_name: ModelName):
    if model_name is ModelName.alexnet:
        return {"model_name": model_name, "message": "Deep Learning FTW!"}
    return {"model_name": model_name}

Query Parameters

Basic Query Parameters

@app.get("/items/")
def read_items(skip: int = 0, limit: int = 10):
    return {"skip": skip, "limit": limit}

# Optional parameters
@app.get("/items/{item_id}")
def read_item(item_id: int, q: str | None = None):
    if q:
        return {"item_id": item_id, "q": q}
    return {"item_id": item_id}

Required Query Parameters

@app.get("/search/")
def search(q: str):  # Required
    return {"query": q}

Request Body

Pydantic Models

from pydantic import BaseModel, EmailStr
from typing import Optional

class UserCreate(BaseModel):
    name: str
    email: EmailStr
    password: str
    age: Optional[int] = None

class UserResponse(BaseModel):
    id: int
    name: str
    email: EmailStr

    class Config:
        from_attributes = True

@app.post("/users/", response_model=UserResponse)
def create_user(user: UserCreate):
    # Save to database...
    return {"id": 1, "name": user.name, "email": user.email}

Validation

from pydantic import BaseModel, Field, validator

class Item(BaseModel):
    name: str = Field(..., min_length=1, max_length=100)
    price: float = Field(..., gt=0)
    quantity: int = Field(default=1, ge=0, le=1000)
    description: str | None = Field(default=None, max_length=500)

    @validator('name')
    def name_must_be_valid(cls, v):
        if not v.strip():
            raise ValueError('Name cannot be empty')
        return v.strip()

@app.post("/items/")
def create_item(item: Item):
    return item

Response Models

Multiple Response Models

from typing import List

class ItemBase(BaseModel):
    name: str
    price: float

class ItemCreate(ItemBase):
    pass

class ItemResponse(ItemBase):
    id: int

    class Config:
        from_attributes = True

@app.get("/items/", response_model=List[ItemResponse])
def get_items():
    return [
        {"id": 1, "name": "Item 1", "price": 100},
        {"id": 2, "name": "Item 2", "price": 200}
    ]

Status Codes

from fastapi import status

@app.post("/items/", status_code=status.HTTP_201_CREATED)
def create_item(item: Item):
    return item

@app.delete("/items/{item_id}", status_code=status.HTTP_204_NO_CONTENT)
def delete_item(item_id: int):
    return None

Routers

Organize Routes

# routers/users.py
from fastapi import APIRouter

router = APIRouter(
    prefix="/users",
    tags=["users"]
)

@router.get("/")
def get_users():
    return [{"id": 1, "name": "Budi"}]

@router.get("/{user_id}")
def get_user(user_id: int):
    return {"id": user_id, "name": "Budi"}

# main.py
from fastapi import FastAPI
from routers import users

app = FastAPI()
app.include_router(users.router)

Database Integration

SQLAlchemy Setup

# database.py
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

SQLALCHEMY_DATABASE_URL = "sqlite:///./app.db"

engine = create_engine(
    SQLALCHEMY_DATABASE_URL,
    connect_args={"check_same_thread": False}
)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
Base = declarative_base()

def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()

Models

# models/user.py
from sqlalchemy import Column, Integer, String
from database import Base

class User(Base):
    __tablename__ = "users"

    id = Column(Integer, primary_key=True, index=True)
    name = Column(String, index=True)
    email = Column(String, unique=True, index=True)
    hashed_password = Column(String)

CRUD Operations

from fastapi import Depends
from sqlalchemy.orm import Session
from database import get_db
from models.user import User

@app.get("/users/")
def get_users(db: Session = Depends(get_db)):
    users = db.query(User).all()
    return users

@app.post("/users/")
def create_user(user: UserCreate, db: Session = Depends(get_db)):
    db_user = User(
        name=user.name,
        email=user.email,
        hashed_password=hash_password(user.password)
    )
    db.add(db_user)
    db.commit()
    db.refresh(db_user)
    return db_user

Authentication

JWT Authentication

from datetime import datetime, timedelta
from jose import JWTError, jwt
from passlib.context import CryptContext

SECRET_KEY = "your-secret-key"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30

pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

def create_access_token(data: dict):
    to_encode = data.copy()
    expire = datetime.utcnow() + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    to_encode.update({"exp": expire})
    return jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)

def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)

def get_password_hash(password):
    return pwd_context.hash(password)

Protect Routes

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")

async def get_current_user(token: str = Depends(oauth2_scheme)):
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise HTTPException(status_code=401, detail="Invalid token")
    except JWTError:
        raise HTTPException(status_code=401, detail="Invalid token")

    user = get_user(username)
    if user is None:
        raise HTTPException(status_code=401, detail="User not found")
    return user

@app.get("/protected/")
async def protected_route(current_user: User = Depends(get_current_user)):
    return {"message": f"Hello {current_user.name}"}

Error Handling

HTTPException

from fastapi import HTTPException

@app.get("/items/{item_id}")
def get_item(item_id: int):
    if item_id not in items:
        raise HTTPException(
            status_code=404,
            detail="Item not found",
            headers={"X-Error": "Item does not exist"}
        )
    return items[item_id]

Custom Exception Handler

from fastapi import Request
from fastapi.responses import JSONResponse

class CustomException(Exception):
    def __init__(self, name: str):
        self.name = name

@app.exception_handler(CustomException)
async def custom_exception_handler(request: Request, exc: CustomException):
    return JSONResponse(
        status_code=418,
        content={"message": f"Oops! {exc.name} did something wrong."}
    )

Middleware

Custom Middleware

from fastapi.middleware.cors import CORSMiddleware
import time

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

# Custom middleware
@app.middleware("http")
async def add_process_time_header(request: Request, call_next):
    start_time = time.time()
    response = await call_next(request)
    process_time = time.time() - start_time
    response.headers["X-Process-Time"] = str(process_time)
    return response

Deployment

Production Settings

# config.py
from pydantic_settings import BaseSettings

class Settings(BaseSettings):
    app_name: str = "My API"
    debug: bool = False
    database_url: str
    secret_key: str

    class Config:
        env_file = ".env"

settings = Settings()

Docker

FROM python:3.11-slim

WORKDIR /app

COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

COPY . .

CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]

Kesimpulan

FastAPI adalah framework modern yang ideal untuk building APIs. Auto-documentation dan type validation membuat development lebih cepat dan aman.