Django Interview Questions and Answers

Django is a high level web development framework in python to develop a web application in python programming language..

Features available in Django are

• It is free and high API
• Admin Interface (CRUD)
• Templating
• Form handling
• Internationalization
• Automatic database table creation
• Easy database migrations
• Session, user management, role-based permissions
• A powerful cache framework for dynamic websites
• Object-relational mapping (ORM)
• Testing Framework
• Syndication feed framework
• Internationalization
• Better Security features
• Elegant URL design
• Other helpful add-ons
• Cache System
• Easy Documentation

Django follows Model-View Controller (MVC) architectural pattern.

Setting Session in Django

request.session[‘key’] = ‘value’

Unset Session in Django

del request.session[‘key’]

Django is based on MVC architecture. It contains the following layers:

Models: It describes the database schema and data structure.

Views: The view layer is a user interface. It controls what a user sees, the view retrieves data from appropriate models and execute any calculation made to the data and pass it to the template.

Templates: It determines how the user sees it. It describes how the data received from the views should be changed or formatted for display on the page.

Controller: Controller is the heart of the system. It handles requests and responses, setting up database connections and loading add-ons. It specifies the Django framework and URL parsing.

Django can be broken into many components:

Models.py file: This file defines your data model by extending your single line of code into full database tables and add a pre-built administration section to manage content.

Urls.py file: It uses regular expression to capture URL patterns for processing.

Views.py file: It is the main part of Django. The actual processing happens in view.

When a land on Django page, first Django checks the URLs pattern you have created and uses information to retrieve the view. After that view processes the request, querying your database if necessary, and passes the requested information to template.

After that the template renders the data in a layout you have created and displays the page.

• It allows you to divide code modules into logical groups to make it flexible to change
• To ease the website administration, it provides auto-generated web admin
• It provides pre-packaged API for common user tasks
• It gives you template system to define HTML template for your web page to avoid code duplication
• It enables you to define what URL be for a given function
• It enables you to separate business logic from the HTML
• Everything is in python

• It facilitates you to divide code modules into logical groups to make it flexible to change.
• It provides auto-generated web admin to make website administration easy.
• It provides pre-packaged API for common user tasks.
• It provides template system to define HTML template for your web page to avoid code duplication.
• It enables you to define what URL is for a given function.
• It enables you to separate business logic from the HTML.

To start a project in Django, you use command $ django-admin.py and then use the command

Project

_init_.py

manage.py

settings.py

urls.py

Ans6: You can use the command edit mysite/setting.py , it is a normal python module with module level representing Django settings.

Django uses SQLite by default; it is easy for Django users as such it won’t require any other type of installation. In the case your database choice is different that you have to the following keys in the DATABASE ‘default’ item to match your database connection settings

Engines: you can change database by using ‘django.db.backends.sqlite3’, ‘django.db.backeneds.mysql’, ‘django.db.backends.postgresql_psycopg2’, ‘django.db.backends.oracle’ and so on

Name: The name of your database. In the case if you are using SQLite as your database, in that case database will be a file on your computer, Name should be a full absolute path, including file name of that file.

If you are not choosing SQLite as your database then setting like Password, Host, User, etc. must be added.

• Python Int
• Python Float
• Python Complex
• Python Boolean
• Python Dictionary
• Python List
• Python Tuple
• Python Strings
• Python Set

Every data type in python language is internally implemented as a class

Python language data types are categorized into two types.

They are::

• Fundamental Types
• Collection Types

Signal are inbuilt utility in Django. They allow to execute some piece of code based on some action or event is occurred in framework something like a new user register, on delete of a record.

Below is the list of some inbuilt signal in Django.

pre_save and post_save.

pre_delete and post_delete

pre_request and post_request

pre_request and post_request

There are three main things required to set up static files in Django

• Set STATIC_ROOT in settings.py
• run manage.py collectsatic
• set up a Static Files entry on the PythonAnywhere web tab

The template is a simple text file.  It can create any text-based format like XML, CSV, HTML, etc.  A template contains variables that get replaced with values when the template is evaluated and tags (% tag %) that controls the logic of the template.

In Django, the session framework enables you to store and retrieve arbitrary data on a per-site-visitor basis.  It stores data on the server side and abstracts the receiving and sending of cookies.  Session can be implemented through a piece of middleware.

To use file based session you have to set the SESSION_ENGINE settings to “django.contrib.sessions.backends.file”

Migration in Django is to make changes to your models like deleting a model, adding a field, etc. into your database schema.  There are several commands you use to interact with migrations.

• Migrate
• Makemigrations
• Sqlmigrate

To do the migration in SQL, you have to print the SQL statement for resetting sequences for a given app name.

django-admin.py sqlsequencreset

Use this command to generate SQL that will fix cases where a sequence is out sync with its automatically incremented field data.

To load data into Django you have to use the command line Django-admin.py loaddata. The command line will search the data and loads the contents of the named fixtures into the database.

This command line executes over the entire source tree of the current directory and abstracts all the strings marked for translation.  It makes a message file in the locale directory.

In Django, there is three possible inheritance styles

Abstract base classes: This style is used when you only want parent’s class to hold information that you don’t want to type out for each child model

Multi-table Inheritance: This style is used If you are sub-classing an existing model and need each model to have its own database table

Proxy models: You can use this model, If you only want to modify the Python level behaviour of the model, without changing the model’s fields

Field class types determines

• The database column type
• The default HTML widget to avail while rendering a form field
• The minimal validation requirements used in Django admin and in automatically generated forms

Django officially supports four database backends, they are

• Oracle
• PostgreSQL
• MySQL
• SQLite

In addition to these, you can also use following 3rd parties

• SAP SQL Anywhere
• ODBC
• IBM DB2
• Microsoft SQL Server
• Firebird

The Django field class types specify:

• The database column type.
• The default HTML widget to avail while rendering a form field.
• The minimal validation requirements used in Django admin.
• Automatic generated forms.

Django-admin.py: It is a Django’s command line utility for administrative tasks.

Manage.py: It is an automatically created file in each Django project. It is a thin wrapper around the Django-admin.py. It has the following usage:

It puts your project’s package on sys.path.

It sets the DJANGO_SETTING_MODULE environment variable to points to your project’s setting.py file.

Middleware is a function that acts on or transforms a request/response before/after it passes through the view layer (e.g. adding the user object to the request)

Some usage of middlewares in Django is:

It can be used for Session management,

User authentication can be done with the help of this.

It helps in Cross-site request forgery protection

Content Gzipping, etc.

Two important parameters in signals are:

Receiver: It specifies the callback function which will be connected to the signal.

Sender: It specifies a particular sender to receive signal from.

• Youtube
• Google
• Instagram
• Quora
• Pinterest
• Mozilla Firefox
• Disqus
• Bitbucket
• NASA
• Onion
• Reddit
• The Washington Post
• Eventbrite
• Mahalo

Flask is a micro framework primarily builds for a small application with simpler requirements. In flask, you have to use external libraries. Flask is ready to use.

Pyramid is built for larger applications. It provides flexibility and lets the developer use the right tools for their project. The developer can choose the database, URL structure, templating style and more. Pyramid is heavy configurable. Django can also used for larger applications just like Pyramid. It includes an ORM.