Python Flask Interview Questions For Freshers & Experienced

Python Flask is popular, extensible micro web framework written building web applications using Python Programming Language. This does not require particular tools or libraries and does not have database abstraction layer, form validation, or any other components.

You can use python flask framework for creating API's, blog or wiki-like platform.

A Single Flask module in the project is structured as below

app.py
config.py
requirements.txt
static/
templates/

You can use the below command to install Python Flask.

pip install Flask

A simple Flask application looks like below

from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello, World!'

You can start python flask app by running below command

$ export FLASK_APP=hello.py
$ flask run
 * Running on http://127.0.0.1:5000/

Flask g name stands for "global" which is referring to data being global within a context. The data saved in g is lost after the context ends, and it is not an appropriate place to store data between requests.

Run below command to check the installed version of the python flask

>> import flask
>> flask.__version__

Django, Sinatra, Pyramid, Falcon framework, Bottle, jam-py are some good alternatives to Python Flask.

App routing in Flask is used to map a specific URL with the associated function that is intended to perform some task.

Set app.debug to True and add below code in your function where you want to enable logging in Flask.

import logging
from flask import Flask
app = Flask(__name__)

@app.route('/')
def foo():
    app.logger.warning('A warning occurred')
    app.logger.error('An error occurred')
    app.logger.info('Info')
    return "foo"

You can use redirect() to redirect to a URL in python flask.

Example:

return redirect("http://www.example.com", code=301)

Query Parameter also known as query strings in Python Flask are post or get data that is send to the server via form or ajax method. You can use request.args.get('query_name') function to get a query string in Flask Framework.

You can use Model.query.all() method to get all records for the table in Flask.

Example

@app.route('/users')
def users():
    users = User.query.all()  

Use jsonify() function to return json in flask.

Example

from flask import jsonify
@app.route('/users')
def users():
   users= User.query.all()  
    return jsonify(users)

Flask macro is a tool to build modular user interface on web pages.