Interview.md

Flask & Python Interview Q&A

1. What is Flask? Why is it called a microframework?

• Flask is a lightweight Python web framework used to build web apps and APIs.
• It’s called a microframework because it only provides essentials (routing, request/response) and relies on extensions for extra features.

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2. Compare Flask, Django, and FastAPI.

• Flask → Lightweight, flexible, minimal setup, great for small/medium apps.
• Django → Full-stack, batteries-included (ORM, admin, auth), good for large projects.
• FastAPI → Modern, high-performance, async-based, auto API docs, best for APIs.

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3. What is @app.route() in Flask and why do we use it?

• @app.route() is a decorator that maps a URL to a function.
• Example:

@app.route("/hello")
def hello():
    return "Hello, Flask!"

Visiting /hello runs hello().

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4. What is the difference between path parameters and query parameters in Flask?

• Path parameter → Part of the URL itself. Example: /user/5.
• Query parameter → Passed after ? in the URL. Example: /search?name=suraj.

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5. How do you access query parameters inside a Flask route?

from flask import request

@app.route("/search")
def search():
    name = request.args.get("name")
    return f"Searching for {name}"

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6. What does debug=True do in app.run()?

• Enables debug mode:

  • Shows detailed error messages in browser.
  • Auto-reloads server when code changes.

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7. What is the purpose of the request object in Flask?

• Represents the incoming HTTP request.
• Lets us access form data, query params, JSON, headers, cookies, and HTTP method.

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8. Explain the Request → Response Lifecycle in Flask.

1. Client sends a request (URL + data).
2. Flask matches the request to a route (@app.route).
3. Flask runs the matched view function.
4. Function returns a response (HTML, JSON, text).
5. Flask sends the response back to the client.

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9. What is type hinting in Python? Show an example.

• Type hinting specifies the expected types of variables/returns in a function.

def add(x: int, y: int) -> int:
    return x + y

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10. Write a Python function to check if a number is prime.

def is_prime(n: int) -> bool:
    if n < 2:
        return False
    for i in range(2, int(n**0.5) + 1):
        if n % i == 0:
            return False
    return True

print(is_prime(7))   # True
print(is_prime(10))  # False