Web Development: Flask / FastAPI Basics

8. Practice Problems

1. Sketch a Flask app with / returning HTML and /api/ping returning JSON.
   Flask app sketch করুন — / HTML দেবে, /api/ping JSON।
   ✨ Show Answer (উত্তর দেখুন)

   ans1.py

   from flask import Flask, jsonify
   app = Flask(__name__)
   
   @app.route("/")
   def home():
       return "<h1>hi</h1>"
   
   @app.route("/api/ping")
   def ping():
       return jsonify({"ok": True})
   
   print("run locally with: flask --app ans1 run")

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2. Sketch a FastAPI endpoint that takes a name query param and returns a greeting.
   FastAPI endpoint লিখুন — query param name নিয়ে greeting দেবে।
   ✨ Show Answer (উত্তর দেখুন)

   ans2.py

   from fastapi import FastAPI
   app = FastAPI()
   
   @app.get("/greet")
   def greet(name: str = "world"):
       return {"msg": f"hello, {name}"}
   
   print("run: uvicorn ans2:app --reload")

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3. In two sentences, explain why FastAPI is often preferred for new APIs.
   দুই বাক্যে বলুন — নতুন API-এ FastAPI কেন prefer করা হয়।
   ✨ Show Answer (উত্তর দেখুন)

   Answer: FastAPI uses Python type hints and Pydantic to validate inputs and auto-generate interactive OpenAPI docs — you get robust request parsing and documentation essentially for free. It is also async-native, so I/O-heavy endpoints (DB, external APIs) scale far better than a synchronous Flask app for equivalent hardware.

   FastAPI Python type hint ও Pydantic দিয়ে input validate করে এবং auto-generate করে OpenAPI interactive docs — request parsing ও documentation প্রায় বিনামূল্যে মেলে। এটি async-native, তাই I/O-heavy endpoint (DB, external API) সমান হার্ডওয়্যারে synchronous Flask-এর চেয়ে অনেক ভালো scale করে।

4. Describe what goes into a minimal production deployment of a Flask app.
   Flask app-এর minimal production deployment-এ কী কী লাগে?
   ✨ Show Answer (উত্তর দেখুন)

   1) gunicorn WSGI server, 2) nginx reverse proxy with TLS, 3) Dockerfile + a pinned requirements.txt, 4) env-var configuration, 5) external DB (PostgreSQL), 6) basic logging and an error tracker (Sentry), 7) a domain pointing at the load balancer. Most cloud providers (Fly.io, Railway, Render) give you these in one click.

5. Write a pydantic model for an Item(name, price, in_stock).
   Item(name, price, in_stock) — pydantic model লিখুন।
   ✨ Show Answer (উত্তর দেখুন)

   ans5.py

   from pydantic import BaseModel
   
   class Item(BaseModel):
       name: str
       price: float
       in_stock: bool = True
   
   i = Item(name="rice", price=75.0)
   print(i.model_dump())

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