🧠 FastAPI — Quick Summary

🚀 Overview

FastAPI is a modern, high-performance web framework for building RESTful APIs with Python 3.7+.
Built on Starlette (for web parts) and Pydantic (for data validation).
Known for its speed, type hints, and automatic documentation.

⚙️ Key Features

• Asynchronous support: Built-in support for async/await.
• Data validation & serialization: Handled automatically via Pydantic models.
• Automatic interactive docs: Swagger UI (/docs) and ReDoc (/redoc).
• Dependency Injection: Clean handling of dependencies and middleware.
• Type hinting: Ensures better autocompletion and error checking.
• Performance: Comparable to Node.js and Go for API speed.

📘 Basic Structure

from fastapi import FastAPI

app = FastAPI()

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

Run server:

uvicorn main:app --reload

Method	Description
GET	Retrieve data
POST	Create new resource
PUT	Update existing resource
DELETE	Remove resource

🧱 Pydantic Models (Data Validation)

from pydantic import BaseModel

class Course(BaseModel):
    id: int
    name: str
    duration: int

Use it in endpoints:

@app.post("/courses")
def add_course(course: Course):
    return course

🧰 Useful Features

• Path parameters: /courses/{id}
• Query parameters: /courses?category=math
• Request body: Automatic JSON parsing
• Response models: Define output schemas
• Exception handling: Use HTTPException for custom error responses
• Middleware & CORS: Add easily for authentication or cross-origin support

Example – Using HTTPException:

from fastapi import HTTPException

@app.get("/courses/{id}")
def get_course(id: int):
    course = {"id": 1, "name": "Python"}  # example data
    if id != course["id"]:
        raise HTTPException(status_code=404, detail="Course not found")
    return course

🧾 Auto Documentation

• Swagger UI: http://127.0.0.1:8000/docs
• ReDoc: http://127.0.0.1:8000/redoc

📦 Common Commands

pip install fastapi uvicorn
uvicorn main:app --reload