Setting Up a Hello World Python Project with JWT Middleware Using FastAPI

If you're just starting with FastAPI and want a clean, simple project that includes user authentication via JWT (JSON Web Tokens), this post walks you through setting it up step-by-step—from creating your virtual environment to serving your app locally.

🧱 Step 1: Initialize the Project Structure

First, create a new folder for your project:

mkdir fastapi-hello-jwt
cd fastapi-hello-jwt

Create some basic structure:

touch main.py
mkdir app
touch app/__init__.py app/auth.py

🐍 Step 2: Set Up Virtual Environment

Let’s isolate dependencies using venv:

python3 -m venv venv
source venv/bin/activate  # On Windows use `venv\Scripts\activate`

Install FastAPI and Uvicorn:

pip install fastapi uvicorn python-jose[cryptography] passlib[bcrypt]

Freeze the requirements:

pip freeze > requirements.txt

👋 Step 3: Build the Hello World Endpoint

Edit main.py:

from fastapi import FastAPI
from app.auth import get_current_user

app = FastAPI()

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

@app.get("/protected")
def protected_route(user: str = Depends(get_current_user)):
    return {"message": f"Hello, {user}!"}

🔐 Step 4: Create Basic JWT Middleware (in `app/auth.py`)

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from jose import JWTError, jwt
from datetime import datetime, timedelta

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

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")

def create_access_token(data: dict, expires_delta: timedelta = None):
    to_encode = data.copy()
    expire = datetime.utcnow() + (expires_delta or timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES))
    to_encode.update({"exp": expire})
    return jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)

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")
        return username
    except JWTError:
        raise HTTPException(status_code=401, detail="Invalid token")

🔁 Step 5: Add a Token Route for Testing

In main.py, add this route:

from fastapi.security import OAuth2PasswordRequestForm
from app.auth import create_access_token

@app.post("/token")
def login(form_data: OAuth2PasswordRequestForm = Depends()):
    if form_data.username == "admin" and form_data.password == "admin":
        token = create_access_token({"sub": form_data.username})
        return {"access_token": token, "token_type": "bearer"}
    raise HTTPException(status_code=401, detail="Invalid credentials")

▶️ Step 6: Run and Serve the App

With everything set, you can run your app using Uvicorn:

uvicorn main:app --reload

Now:

GET / returns a public "Hello, World!"
POST /token with body username=admin&password=admin gives you a JWT
GET /protected requires a Bearer token

✅ Final Notes

Keep your SECRET_KEY safe and use environment variables in real apps.
This is a starting point—you should add user management, proper hashing, and token refresh logic for production.