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VOOZH | about |
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VOOZH | about |
Flask is a lightweight Python web framework used to build web applications. These questions will help you prepare for Flask developer interviews.
Answer: Flask is a micro web framework in Python for building web applications. It is based on WSGI and uses the Jinja2 template engine. Flask is flexible, easy to learn, and provides visual debugging for better control during development.
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Flask | Django |
Flask is a WSGI framework | Django is a Full-stack web framework |
It allows multiple types of databases. | It doesn't support multiple types of databases. |
Use SQL Alchemy | Build-in ORM |
Diversified Working Style | Monolithic Working Style |
Arbitrary structure | Conventional Project Structure |
It supports API | It does not have any support for API |
It does not support Dynamic HTML pages | Django accepts Dynamic Pages. |
It has support for Visual debug | No support for Visual Debug |
It doesn't offer a built-in bootstrapping tool. | Django-admin enables us to start building web applications |
URL dispatcher is a RESTful request. | URL dispatcher is Robust Documentation. |
Answer: The default local host of the flask is 127.0.0.1, and the default port is 5000.
Answer: Flask supports SQLite, MySQL, PostgreSQL, Oracle, and other SQL databases using Flask-SQLAlchemy. For NoSQL databases like MongoDB, Flask can connect using Flask-MongoEngine. DbAdapters help Flask work with different databases easily.
Answer: The __name__ parameter is a Python built-in variable that is set to the name of the current module. When we pass __name__ as an argument to the Flask class constructor, it helps Flask to determine where to locate resources such as templates and static files.
Answer: App Routing means mapping the URLs to a specific function that will handle the logic for that URL. Modern web frameworks use more meaningful URLs to help users remember the URLs and make navigation simpler.
So if our site’s domain was www.example.org and we want to add routing to “www.example.org/hello”, we would use “/hello”.
Answer: Template Inheritance in Flask’s Jinja allows you to define common elements (like headers, footers, or navigation bars) once in a base template and reuse them across multiple pages. This avoids repeating HTML code and makes templates easier to maintain.
Answer: The url_for() function generates a URL for a given function dynamically. It allows passing arguments to fill URL variables, so you don’t need to hard-code URLs in templates.
Example:
<a href="{{ url_for('get_post_id', post_id=post.id) }}">{{ post.title }}</a>
View function for handling variables in routes.
@app.route(“/blog/post/<string:post_id>”)
def get_post_id(post_id):
return post_id
Answer: In Flask, cookies are handled using the set_cookie() method on the response object. Cookies store small pieces of data on the client’s browser and are sent back to the server with each request. They are often used to track user actions, preferences, or sessions.
Answer: In Flask, file uploading is done via an HTML form with enctype="multipart/form-data". The uploaded file is accessed on the server using request.files[] and can be saved to a desired location.
Example
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!"
This saves the uploaded file to the uploads folder on the server.
Answer: WTF, also known as WT Forms in Flask, is a type of interactive user interface. The WTF is a flask built-in module that lets you build forms in a different way in flask web apps. Flask-WTF is designed to be simple to connect with WTForms, and it works well with Flask-WTF. Flask WTF includes the following features:
Answer: In Flask Python, An identifier can be as long as you want, as python is case-sensitive so it will treat upper case and lower case letters differently. Also, there are some words that are reserved keywords that can't be used by users. Some of them are listed below:
def, false, import, not, true, as, del, finally, in, or, try, assert, elseif, for, is, pass, while, break, else, from, lambda, print, with, class, except, global, none, raise, yield, continue, exec, if, nonlocal, return
There are also some standards that users must follow while naming an identifier. It should start with a character, underscore, or a letter from A to Z or a-z, and the remaining characters in the identifier's name can be any of the following: A-Z or a-z, 0-9, or.
Answer: To handle HTTP requests, Flask uses a number of decorators. The HTTP protocol is the backbone of internet data communication. This HTTP protocol defines a number of techniques for obtaining information from a particular URL. The different HTTP methods are:
| Request | Purpose |
|---|---|
| GET | The most widely used approach. The server responds with data after receiving a GET message. |
| POST | To submit HTML form data to the server, use this method. The server does not save the data supplied via the POST method. |
| PUT | Upload content to replace all current representations of the target resource. |
| DELETE | Deletes all current representations of the URL's target resource. |
| HEAD | Retrieves the headers for a resource, without retrieving the resource itself. |
Answer: Template engines help build web applications by separating HTML structure from Python code. They allow you to render dynamic content (like body, navigation, footer) on the server before sending it to the browser.
Popular template engines: Jinja2 (Flask), EJS, Pug, Mustache, HandlebarsJS, Blade.
Answer: jsonify() converts Python data to JSON and returns it as a response with the correct application/json content type. It simplifies creating APIs by automatically setting headers and formatting the data properly, unlike json.dumps() which only returns a JSON string.
Answer: Flask sessions let you store data between client requests on the server. The session object can save user-specific information, like login details.
Example:
Answer: Opening and closing database connections for every request is inefficient. Flask provides decorators to manage connections for a single request:
Answer: The g object in Flask is a global namespace that stores data only for the current request, allowing different functions within the same request to access it, for example, g.user and session object stores data across multiple requests for a specific user or browser, persisting until it expires or is cleared. The main difference is that g is request-specific, while session is user-specific and persists across requests.
Answer: When Debug is turned on, any changes to the application code are updated immediately in the development stage, eliminating the need to restart the server.
#Method 1
app.debug = True
#Method 2
app.run('host' = localhost, debug = True)
Answer: A thread-local object is one that is connected to the current thread id and saved in a specialized structure. Internally, Flask Python uses thread-local objects so that the user does not have to transmit objects from one function to the next within a request to stay thread safe.
Answer: In a flask, Memory allocation is managed by the Flask Python memory management. Also, It has an inbuilt garbage collector which recycles all unused memory to save up heap space. The Python interpreter's responsibility is to keep track of everything. Users can, however, use the core API to access some of the tools.
Answer: Flask is versatile and can be used to build almost any type of web application. It works well with other technologies like NodeJS, AWS Lambda, and third-party services. You can create Single Page Applications, RESTful APIs, SaaS apps, small to medium websites, static websites, machine learning apps, microservices, and serverless applications.
Answer: Flask Restful is a Flask plugin that allows you to create REST APIs in Python using Flask as the backend. To create a REST API, we have to do the following steps:
Answer: Sijax is a Python/jQuery library that makes AJAX easy to use in web applications to your Flask applications. Flask Sijax also provides an easy way to send JSON data between the server and the client.
To install we can use the following command:
pip install flask-sijax
Answer: Flask is called a microframework because it has a small core with only essential features like routing, request handling, and blueprints. Other features such as ORM, authentication, and caching are available through optional extensions. This “small core + extensions” design makes Flask lightweight, easy to learn, and flexible to scale.
Answer: To get the visitor IP address in Flask we use method request.remote_addr Below is the implementation of it:
Answer: Extension enhances database management and interaction during development by eliminating the requirement to write raw SQL queries. PostgreSQL, SQLite, and MySQL are just a few of the RDBMSs Flask supports. The Flask-SQLAlchemy plugin is required to connect to databases.
Answer: Logging in Flask allows developers to track events and errors in their applications. It uses Python’s standard logging framework, providing flexibility to create custom logs and monitor application behavior effectively.
Answer: The Application Context is the context in which the Flask application runs. It is created when the application starts and is destroyed when the application when us down. The application context stores the configuration and another global state of the application.
The Request Context is the context in which a request is processed. It is created when a request comes in and is destroyed when the request is completed. The Request Context stores information about the current request, such as the request method, URL, headers, and form data.
Answer: Flask-SocketIO is a Flask extension that provides real-time communication between clients and servers using WebSockets.
Answer: Flask-Bcrypt is a Flask extension that provides password hashing and verification functionality for Flask applications.
Answer: Flask-JWT is a Flask extension that provides JSON Web Token (JWT) authentication and authorization functionality for Flask applications.
Answer: Flask-Assets is a Flask extension that provides tools for managing and compiling static assets like CSS and JavaScript files.
Answer: Flask-Migrate is a Flask extension that provides database migration functionality for Flask applications.
Answer: Flask-Admin is a Flask extension that provides a simple interface for building administrative interfaces for Flask applications. It allows you to quickly and easily create CRUD (Create, Read, Update, Delete) interfaces for your application's models and data.
Answer: Flask-SQLAlchemy is a Flask extension that provides an easy-to-use interface for working with SQL databases in Flask applications.
Answer: You can handle errors in Flask by using Flask's error-handling functionality. This allows you to define custom error pages and handlers for different types of errors.
Answer: A Flask blueprint is a way to structure an application into smaller, modular components. It allows you to define routes, templates, and static files separately, which can then be registered with the main application to build a larger, organized project.
Answer: Flask-RESTful is a Flask extension that simplifies building RESTful APIs. It provides tools to define API endpoints, handle HTTP methods, serialize data, and manage responses, making it easier to create structured and maintainable APIs in Flask applications.
