FastAPI — Web APIs

Introduction

FastAPI is the modern Python web framework: async, type-driven, auto-generates OpenAPI docs. Built on Starlette + Pydantic.

Understanding the topic

Core concepts to understand:

• Type-hint params → automatic validation.
• Async by default.
• Auto /docs (Swagger UI), /redoc.
• Pydantic models = request/response schemas.

Syntax reference

Visual flow / code:

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

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

@app.get("/items/{item_id}")
async def get_item(item_id: int) -> Item:
    return Item(name="Book", price=9.99)

@app.post("/items")
async def create(item: Item) -> Item:
    return item

# Run
# uvicorn main:app --reload

Execution workflow

Real-world use

FastAPI is now the #1 Python framework for new APIs — used by Netflix, Microsoft, Uber. Beats Flask/Django for type safety and performance.

Best practices

• Use Pydantic models for every request/response.
• Always type your handlers.
• Run with uvicorn + gunicorn in prod.

Hands-on exercise

Interview preparation — practice these questions:

• FastAPI vs Flask vs Django?
• What is Pydantic?
• Why is FastAPI fast?

Summary

In summary: Type-driven, async, auto-docs. Default choice for new Python APIs.