CodeSubmit Interview Series

The 9 Best Flask Interview Questions in 2023

What are the top Flask interview questions? Today, you’ll get the best Flask interview questions to use at your next interview. Want to learn more? Read on! 

Interviewing Flask developers 

How do you find the best Flask developers? 

Flask is a microweb framework written in Python that doesn’t require any particular tools or libraries. What's more, it doesn’t have any components where pre-existing third-party libraries provide common functions. 

But how do you identify the best Flask developers? Use the interview questions here below to do just that. The skills you should look out for are Python and Flask, so focus on asking relevant questions to gauge your candidates' skills.

Want to learn more? Read on!

Beginner Flask interview questions

What are the top junior Flask developer interview questions? Here are the top Flask questions to ask at your next interview. 

1. What are the advantages of the Flask framework? 


Flask and Python include several similar advantages. 

  • Flask is modular and lightweight. In other words, it transforms into web applications or frameworks when a few lightweight extensions are needed.  

  • Flask is flexible and gives users a lot of options 

  • Deploying Flask is easy; Flask includes 100% WSGI 1.0 support. 

  • Users can plug in different ORMs because Flask is ORM agnostic. 

  • The Flask API foundation is nicely shaped and coherent. 

  • Flask is comprehensively documented and well-structured. 

  • Flask handles HTTP requests effectively. 

2. Explain template engines in Flask. 


Changing the style of a website can be a tedious task. For websites with just a few pages, the process isn’t too time-consuming. But for websites with plenty of pages, there can be a lot of manual work. 

That’s where templates can be helpful. Templates enable you to set a basic layout for all the pages and choose which elements are frequently updated. For instance, you can define the header once and keep it consistent throughout the website. This makes it faster and easier to maintain and update a website. 

3. Describe the most important Flask features.


Flask has several beneficial features, including: 

  • A built-in development server 

  • A fast debugger

  • Integrated support for unit testing

  • Includes the Jinja2 templating technique 

  • Includes the feature of restful request dispatching 

  • Supports secure cookies 

  • Includes WSGI 1.0 compliant features 

  • Is based on Unicode 

  • Is extensively documented 

4. How can you enable debugging in Flask? 


You can debug in Flask in two ways. You can either set the flag on the application object or you can pass the flag as a parameter to run. 

5. Explain the difference between Django and Flask. 


Similar to Flask, Django is a web development framework created with Python. It’s older and more mature than Flask with a lot of features such as an ORM with migration capability and an admin backend. 

Flask is a better option when you need to prototype or develop something quickly. It’s a better fit for lightweight web applications that don’t require a large codebase, microservices, or serverless applications. Flask is also easier to learn and has fewer APIs than Django. 

Advanced Flask interview questions

What are the top advanced Flask interview questions? Here’s what you need to know. 

6. Explain how long an identifier can be in Flask. 


An identifier can be of any length in Flask. However, you must follow specific rules to name an identifier. First, it should begin with a character or an underscore or from A-Z or a-z. Second, the rest of the name has to contain any of the following: A-Z or a-z or 0-9 or _.

Flask treats uppercase and lowercase letters differently. Furthermore, certain words (Flask keywords) can’t be used as identifiers. These include: pass, while, break, else, from, lambda, with, class, except, global, none, raise, in, finally, as, true, false, import, and, def. 

7. Explain the HTTP methods used in Flask. 


Flask uses HTTP methods to retrieve data from an URL. These are: 

  • GET: This is a method that sends data to the server unencrypted. 

  • HEAD: This method is similar to GET, but you don’t have a response body. 

  • POST: The POST server doesn’t cache HTML form data it sends 

  • DELETE: The DELETE method removes current representations of the target resource that are suggested by a URL. 

  • PUT: This method replaces the uploaded content with current data representations of the target resources. 

8. How do you connect to a database in Flask? 


Flask works with most RDBMSs (including PostgreSQL, SQLite, and MySQL). But to use databases, you need to use the Flask-SQLAlchemy extension. This extension makes interaction and management easy during development, but without making it necessary to write raw SQL queries, which are prone to SQL injection attacks. In order to work with No-SQL data stores, such as MongoDB, you can use the Flask-MongoEngine extension. 

9. What does Thread-Local object mean? 


Flasks uses thread local objects to stay thread safe; users don’t have to pass objects around from one function to the other within a request. It does require a pure request context for dependency injection or when you’re attempting to reuse code to use a value indulged in the requests. 

Flask supports database-powered applications like RDBS. However, you need to create a schema and connect a schema.sql file to a sqlite3 command to create or start the database in Flask. 

Over to you!

There you have it! Now you know what the top Flask interview questions are. 

However, interviews are only one part of the assessment process.

You also need to test your candidates’ skills. 

And that’s what CodeSubmit helps you do. Our assessment tests and live coding interviews help you identify the best candidates.

Want to learn more? 

Try CodeSubmit today for free (no credit card required).