Are you wondering what questions might come up in your next Flask interview? We are here to help! In this guide – we have put together 30+ of the most common Flask interview questions and answers to help you feel ready.
Did you know?
Flask is one of the top choices for building Python web apps and is used by big companies like Netflix and LinkedIn.
In fact, as of 2024 – 12.9% of developers around the world use Flask – making it one of the most popular web frameworks.
With Flask’s popularity on the rise – interviewers often look for candidates who know its core concepts well.
So, let’s get started and make sure you’re fully prepared for your interview!
Basic Flask Interview Questions for Freshers
Here are some commonly-asked Flask interview questions and answers for freshers.
- What is Flask?
Flask is a lightweight, flexible web framework for Python. It is designed to help developers build web applications easily by providing basic tools and allowing customization without unnecessary complexity.
- What is the difference between Flask and Django?
This is one of the most important Python Flask interview questions. Here is how you should answer it.
Flask is a micro-framework – meaning it is lightweight and does not come with built-in tools like Django. It offers more flexibility and control to the developer.
Django, on the other hand, is a full-stack framework – which includes features like an ORM, admin interface, and authentication by default. Flask is best for smaller applications, while Django is better for large-scale projects.
- What is a Flask route?
A Flask route is a URL pattern that is mapped to a function. It defines what happens when a user visits a particular URL in the web application.
- What are Flask templates?
Flask templates are HTML files with embedded Jinja2 code that dynamically generate content. They allow you to separate the HTML structure from the Python code.
- What is the Flask request object?
The request object in Flask is used to handle incoming HTTP requests. It contains data from the client, such as form data, query parameters, and cookies. You can use it to access information sent by the user.
- How do you run a Flask application?
To run a Flask application, use the command python app.py in the terminal. This starts the Flask development server, usually accessible at http://127.0.0.1:5000/.
Flask Python Interview Questions – Intermediate Level
Now, let’s take a look at some intermediate level interview questions on Flask and their answers.
- What are Flask blueprints?
Flask blueprints allow you to organize a Flask application into modules – making it easier to manage larger applications. A blueprint defines routes, views, and other functions and can be registered to the main Flask app for modularity and code reuse.
- How does Flask handle sessions?
Flask uses secure cookies to manage sessions. The session object stores data across requests, such as user information, and automatically encrypts the data to ensure security. For example, you can store user login status in the session.
- What is Flask’s g object?
The g object is a global object in Flask used to store data during a request cycle. It is useful for storing data that should be accessible in multiple functions during a single request – such as database connections or user authentication details.
- What are Flask’s request and response hooks?
Flask request and response hooks allow you to run functions before or after a request is processed. For example, before_request can be used to set up session data – while after_request can modify the response before it is sent to the client.
- How can you protect a Flask application from CSRF attacks?
To protect a Flask app from CSRF (Cross-Site Request Forgery) attacks, you can use the Flask-WTF extension. It provides CSRF protection by including a hidden token in forms. This token guarantees that the request comes from a trusted source, not a malicious one.
Flask Interview Questions for Experienced
These are some important Flask interview questions and answers for experienced.
- What is Flask’s application context and request context?
Flask has two contexts: the application context and the request context. The application context is used to manage the lifecycle of the app, while the request context manages the current HTTP request. Both contexts ensure that the app’s resources are properly available when needed during a request cycle.
- How does Flask handle database connections?
Flask does not have a built-in database connection manager. However, developers commonly use extensions like Flask-SQLAlchemy to manage database connections. SQLAlchemy provides tools to handle connection pooling, sessions, and transactions efficiently.
- What are Flask signals, and how do you use them?
Flask signals are used to allow decoupled components to communicate with each other. They provide a mechanism for triggering custom functions when certain events occur in the application, such as before or after a request. Flask uses the blinker library to implement signals.
- How can you deploy a Flask application in production?
To deploy a Flask app in production – you typically use a WSGI server like Gunicorn or uWSGI, behind a reverse proxy like Nginx or Apache. Flask’s built-in server is not suitable for production – so it’s important to set up a proper server configuration for performance and security.
- How do you implement authentication and authorization in Flask?
Flask provides extensions like Flask-Login for handling user authentication and Flask-Principal for authorization. Flask-Login helps manage user sessions – while Flask-Principal is used for role-based access control (RBAC) to protect routes based on user roles or permissions.
Flask Advanced Interview Questions
Here are some advanced level interview questions on Flask Python and their answers.
- How can you improve the performance of a Flask application?
To improve Flask application performance, you can implement techniques like –
- Caching (e.g., using Flask-Caching)
- Optimizing database queries with SQLAlchemy
- Using asynchronous tasks with Celery
- Minimizing the use of synchronous code
- Employing a reverse proxy (e.g., Nginx) for better load balancing and static file handling
- Explain Flask’s request dispatching process.
Flask’s request dispatching process involves several steps: When a request is made, Flask first looks for a matching route based on the URL. If a match is found, the associated view function is executed.
Flask also sets up the request and application contexts to manage the lifecycle of the request and the application state – such as before and after request hooks.
- What is the role of Flask’s teardown_request and teardown_appcontext functions?
teardown_request is used to perform cleanup tasks after each request is processed, regardless of whether the request was successful or not. For example, closing database connections.
teardown_appcontext is used for cleanup after the application context ends, like releasing application-wide resources. Both functions are typically registered using decorators.
Flask REST API Interview Questions
You may also come across some Python Flask REST API interview questions like these.
- How do you create a REST API using Flask?
To create a REST API in Flask, you define routes that handle HTTP methods like GET, POST, PUT, and DELETE. You can use the @app.route() decorator to map these methods to specific functions. JSON is commonly used for data exchange, and Flask’s jsonify helps convert Python dictionaries to JSON format.
- How do you handle errors and exceptions in Flask REST API?
This is one of the most common Flask API interview questions.
In Flask, errors and exceptions can be handled using the @app.errorhandler() decorator to catch specific HTTP errors, such as 404 or 500. You can also use custom exception classes to handle API-specific errors and return appropriate status codes and messages as JSON responses.
- What are Flask-Restful and how does it differ from Flask?
Flask-Restful is an extension that simplifies building REST APIs with Flask. It provides tools like resources and automatic handling of HTTP methods (GET, POST, PUT, DELETE), making it easier to define APIs and handle requests. Unlike Flask, which requires manually handling routes, Flask-Restful abstracts much of the repetitive work for RESTful services.
Django and Flask Interview Questions
Here are some important Flask and Django interview questions and their answers.
- What are the key differences between Flask and Django in terms of project structure?
Flask is minimalistic and doesn’t enforce any project structure. It allows developers to choose their own folder structure, making it more flexible but requiring more setup.
Django, on the other hand, follows a strict project structure with predefined directories for models, views, templates, and static files. This helps in larger applications but can be restrictive for smaller projects.
- How do Flask and Django handle database migrations?
You might also be asked Django Flask interview questions like this one.
Flask typically uses Flask-Migrate with SQLAlchemy to handle database migrations. It integrates with Alembic to manage schema changes and generate migration scripts.
Django has its own built-in system for database migrations through the makemigrations and migrate commands. It can automatically detect and apply schema changes to the database.
- How do Flask and Django handle request and response processing?
In Flask, the request and response cycle is simple – with the view function handling incoming requests and returning a response directly using request and response objects.
In Django, the cycle is more complex, with middleware processing requests before they reach views and responses after. This makes it better suited for larger applications with more complex workflows.
Flask Framework Interview Questions – Coding Related
Let’s take a look at some coding-related Python Flask interview questions and answers.
- How do you create a simple “Hello, World!” app in Flask?
To create a simple Flask app, you define a route using the @app.route() decorator and return a response from a view function:
from flask import Flask
app = Flask(__name__)
@app.route(‘/’)
def hello():
return “Hello, World!”
if __name__ == ‘__main__’:
app.run()
This will start a basic Flask app that responds with “Hello, World!” when the root URL is accessed.
- How can you return JSON data in a Flask route?
To return JSON data, you can use the jsonify() function, which converts Python dictionaries to JSON format:
from flask import Flask, jsonify
app = Flask(__name__)
@app.route(‘/data’)
def data():
return jsonify({“name”: “John”, “age”: 30})
if __name__ == ‘__main__’:
app.run()
This route will return the dictionary as a JSON response.
- How can you handle file uploads in Flask?
You can handle file uploads using request.files and save the file using save() method:
from flask import Flask, request
app = Flask(__name__)
@app.route(‘/upload’, methods=[‘POST’])
def upload_file():
file = request.files[‘file’]
file.save(f”./uploads/{file.filename}”)
return “File uploaded successfully!”
if __name__ == ‘__main__’:
app.run()
This code saves the uploaded file in the “uploads” directory.
Python Flask Questions – MCQs
Here are the common Flask interview questions in MCQ form and their answers.
- Which Flask extension is used for handling forms?
A) Flask-WTF
B) Flask-Forms
C) Flask-Input
D) Flask-Validator
Answer: A) Flask-WTF
- Which function in Flask is used to create a redirect to a specific URL?
A) redirect()
B) url_for()
C) Flask.redirect()
D) redirect_url()
Answer: A) redirect()
- What is the default port for a Flask application when running locally?
A) 8000
B) 8080
C) 5000
D) 4000
Answer: C) 5000
- Which HTTP method does Flask’s @app.route() decorator support by default?
A) GET
B) POST
C) PUT
D) DELETE
Answer: A) GET
- What does the Flask session object store?
A) Data that persists for the entire lifetime of the application.
B) Data that is specific to a user’s current session.
C) Data that is stored in a database.
D) Data related to HTTP headers.
Answer: B) Data that is specific to a user’s current session.
Wrapping Up
Preparing for a Flask interview can be easier when you understand the core concepts and common questions. By practising these 30+ Flask interview questions – you can easily feel more confident in your interview. And hey – if you are still searching for Flask jobs in India – visit Hirist. It is an online job portal where you can easily find the best IT jobs for – interns, freshers as well as experienced professionals.