Setting up FastAPI

🖥️ Step 1: Create Project Folder

🍎 macOS / Linux

mkdir fastapi-project
cd fastapi-project

🪟 Windows

mkdir fastapi-project
cd fastapi-project

🐍 Step 2: Create Virtual Environment

🍎 macOS / Linux

python3 -m venv venv

🪟 Windows

python -m venv venv

This creates a folder named venv/ containing the isolated Python environment.

▶️ Step 3: Activate Virtual Environment

🍎 macOS / Linux

source venv/bin/activate

🪟 Windows

venv\\Scripts\\activate

After activation, your terminal should look like:

(venv) fastapi-project %

That means your virtual environment is active ✅

📦 Step 4: Install FastAPI & Uvicorn

We need:

• FastAPI → Web framework

• Uvicorn → ASGI server to run FastAPI

📌 What is ASGI?

ASGI (Asynchronous Server Gateway Interface) is a standard that allows Python apps to handle:

• HTTP requests

• WebSockets

• Async operations

FastAPI is built on ASGI.

So it needs an ASGI-compatible server to run.

🍎 macOS / Linux

pip install fastapi uvicorn

🪟 Windows

pip install fastapi uvicorn

(Inside virtual environment, pip works correctly on both.)

📁 Step 5: Create Main Application File

Create a file named:

main.py

Add this code:

from fastapi import FastAPI

app = FastAPI()

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

▶️ Step 6: Run the Server

🍎 macOS / Linux

uvicorn main:app --reload

🪟 Windows

uvicorn main:app --reload

🔍 What This Command Means

• main → filename (main.py)

• app → FastAPI instance

• -reload → auto-restarts server on code changes

🌐 Step 7: Open in Browser

Visit:

<http://127.0.0.1:8000>

You should see:

{"message": "Hello, FastAPI 🚀"}