How do Flask and FastAPI web frameworks differ?

Flask and FastAPI are popular web frameworks in Python, but they have different approaches and features:

• Flask is a minimalist and flexible framework that provides a basic set of tools for building web applications. It does not impose a structure and allows developers to choose libraries for database interaction, validation, etc. Flask is well-suited for small to medium projects where simplicity and control are important.

• FastAPI is a modern framework focused on high performance and ease of API development. It uses Python's asynchronous capabilities, automatically generates OpenAPI documentation, and supports data validation via Pydantic. FastAPI is ideal for creating fast and scalable RESTful APIs.

Example of a simple API in FastAPI:

from fastapi import FastAPI

app = FastAPI()

@app.get("/items/{item_id}")
async def read_item(item_id: int):
    return {"item_id": item_id}

In Flask, a similar route would look like:

from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/items/<int:item_id>')
def read_item(item_id):
    return jsonify({"item_id": item_id})