1.What is Django?
Django is a web development framework that was developed in a fast-paced newsroom. It is a free and open-source framework that was named after Django Reinhardt who was a jazz guitarist from the 1930s. Django is maintained by a non-profit organization called the Django Software Foundation. The main goal of Django is to enable Web Development quickly and with ease.
2. Name some companies that make use of Django?
Some of the companies that make use of Django are Instagram, DISCUS, Mozilla Firefox, YouTube, Pinterest, Reddit, etc.
3. What are the features of Django?
•SEO Optimized
•Extremely fast
•Fully loaded framework that comes along with authentications, content administrations, RSS feeds, etc
•Very secure thereby helping developers avoid common security mistakes such as cross-site request forgery (csrf), clickjacking, cross-site scripting, etc
•It is exceptionally scalable which in turn helps meet the heaviest traffic demands
•Immensely versatile which allows you to develop any kind of websites.
4. What are the advantages of using Django?
•Django’s stack is loosely coupled with tight cohesion
•The Django apps make use of very less code
•Allows quick development of websites
•Follows the DRY or the Don’t Repeat Yourself Principle which means, one concept or a piece of data should live in just one place
•Consistent at low as well as high levels
•Behaviors are not implicitly assumed, they are rather explicitly specified
•SQL statements are not executed too many times and are optimized internally
•Can easily drop into raw SQL whenever required
•Flexibility while using URLs.
5. How do you connect your Django project to the database?
Django comes with a default database which is SQLite. To connect your project to this database, use the following commands:
•python manage.py migrate (migrate command looks at the INSTALLED_APPS settings and creates database tables accordingly)
•python manage.py makemigrations (tells Django you have created/ changed your models)
•python manage.py sqlmigrate <name of the app followed by the generated id> (sqlmigrate takes the migration names and returns their SQL).
6. What are ‘Models’?
Models are a single and definitive source for information about your data. It consists of all the essential fields and behaviors of the data you have stored. Often, each model will map to a single specific database table.
In Django, models serve as the abstraction layer that is used for structuring and manipulating your data. Django models are a subclass of the django.db.models.Model class and the attributes in the models represent database fields.
7. What are ‘views’?
Django views serve the purpose of encapsulation. They encapsulate the logic liable for processing a user’s request and for returning the response back to the user. Views in Django either return an HttpResponse or raise an exception such as Http404. HttpResponse contains the objects that consist of the content that is to be rendered to the user. Views can also be used to perform tasks such as read records from the database, delegate to the templates, generate a PDF file, etc.
8. What are ‘templates’?
Django’s template layer renders the information to be presented to the user in a designer-friendly format. Using templates, you can generate HTML dynamically. The HTML consists of both static as well as dynamic parts of the content. You can have any number of templates depending on the requirement of your project. It is also fine to have none of them.
Django has its own template system called the Django template language (DTL). Regardless of the backend, you can also load and render templates using Django’s standard admin.
9. What is the difference between a Project and an App?
An app is basically a Web Application that is created to do something for example, a database of employee records. A project, on the other hand, is a collection of apps of some particular website. Therefore, a single project can consist of an ‘n’ number of apps and a single app can be in multiple projects.
10. What are static files?
Static files in Django are those files that serve the purpose of additional files such as the CSS, images or Javascript files. These files are managed by django.contrib.staticfiles. These files are created within the project app directory by creating a subdirectory named as static.
11. Briefly explain Django Field Class.
‘Field’ is basically an abstract class that actually represents a column in the database table. The Field class is, in turn, a subclass of RegisterLookupMixin. In Django, these fields are used to create database tables (db_type()) which are used to map Python types to the database using get_prep_value() and vice versa using the from_db_value() method. Therefore, fields are fundamental pieces in different Django APIs such as models and querysets.
12. How do you create a Django project?
To create a Django project, cd into the directory where you would like to create your project and type the following command:
•django-admin startproject xyz
NOTE: Here, xyz is the name of the project. You can give any name that you desire.
13. What is mixin?
Mixin is a type of multiple inheritance wherein you can combine behaviors and attributes of more than one parent class. Mixins provide an excellent way to reuse code from multiple classes. For example, generic class-based views consist of a mixin called TemplateResponseMixin whose purpose is to define render_to_response() method. When this is combined with a class present in the View, the result will be a TemplateView class.
One drawback of using these mixins is that it becomes difficult to analyze what a child class is doing and which methods to override in case of its code being too scattered between multiple classes.
14. What are ‘sessions’?
Sessions are fully supported in Django. Using the session framework, you can easily store and retrieve arbitrary data based on the per-site-visitors. This framework basically stores data on the server-side and takes care of sending and receiving cookies. These cookies consist of a session ID but not the actual data itself unless you explicitly use a cookie-based backend.
15. What do you mean by context?
Context in Django is a dictionary mapping template variable name given to Python objects. This is the conventional name, but you can give any other name of your choice if you wish to do it.
16. When can you use iterators in Django ORM?
Iterators in Python are basically containers that consist of a countable number of elements. Any object that is an iterator implements two methods which are, the __init__() and the __next__() methods. When you are making use of iterators in Django, the best situation to do it is when you have to process results that will require a large amount of memory space. To do this, you can make use of the iterator() method which basically evaluates a QuerySet and returns the corresponding iterator over the results.
17. Explain the use of Middlewares in Django.
You may come across numerous Django Interview Questions, where you will find this question. Middleware is a framework that is a light and low-level plugin system for altering Django’s input and output globally. It is basically a framework of hooks into the request/ response processing of Django. Each component in middleware has some particular task. For example, the AuthenticationMiddleware is used to associate users with requests using sessions. Django provides many other middlewares such as cache middleware to enable site-wide cache, common middleware that performs many tasks such as forbidding access to user agents, URL rewriting, etc, GZip middleware which is used to compress the content for browsers, etc.
18. What is the significance of manage.py file in Django?
The manage.py file is automatically generated whenever you create a project. This is basically a command-line utility that helps you to interact with your Django project in various ways. It does the same things as django-admin but along with that, it also sets the DJANGO_SETTINGS_MODULE environment variable in order to point to your project’s settings. Usually, it is better to make use of manage.py rather than the django-admin in case you are working on a single project.
19. Explain the use of ‘migrate’ command in Django?
In Django, migrations are used to propagate changes made to the models. The migrate command is basically used to apply or unapply migrations changes made to the models. This command basically synchronizes the current set of models and migrations with the database state. You can use this command with or without parameters. In case you do not specify any parameter, all apps will have all their migrations running.
20. Explain how a request is processed in Django?
In case some user requests a page from some Django powered site, the system follows an algorithm that determines which Python code needs to be executed. Here are the steps that sum up the algorithm:
•Django first determines which root URLconf or URL configuration module is to be used
•Then, that particular Python module is loaded and then Django looks for the variable urlpatterns
•These URL patterns are then run by Django, and it stops at the first match of the requested URL
•Once that is done, the Django then imports and calls the given view
•In case none of the URLs match the requested URL, Django invokes an error-handling view.
21. How did Django come into existence?
Django basically grew from a very practical need. World Online developers namely Adrian Holovaty and Simon Willison started using Python to develop its websites. As they went on building intensive, richly interactive sites, they began to pull out a generic Web development framework that allowed them to build Web applications more and more quickly. In summer 2005, World Online decided to open-source the resulting software, which is, Django.
22. Explain the Django URLs in brief?
Django allows you to design your own URLs however you like. The aim is to maintain a clean URL scheme without any framework limitations. In order to create URLs for your app, you will need to create a Python module informally called the URLconf or URL configuration which is pure Python code and is also a mapping between the URL path expressions to the Python methods. The length of this mapping can be as long or short as required and can also reference other mappings. When processing a request, the requested URL is matched with the URLs present in the urls.py file and the corresponding view is retrieved.
23. Is Django stable?
Yes, Django is quite stable. Many companies like Instagram, Discus, Pinterest, and Mozilla have been using Django for a duration of many years now. Not just this, Websites that are built using Django have weathered traffic spikes of over 50 thousand hits per second.
24. Does the Django framework scale?
Yes. Hardware is much cheaper when compared to the development time and this is why Django is designed to make full use of any amount of hardware that you can provide. Django makes use of a “shared-nothing” architecture meaning you can add hardware at any level i.e database servers, caching servers or Web/ application servers.
25. Is Django a CMS?
Django is not a CMS (content-management-system) . It is just a Web framework, a tool that allows you to build websites.
26. Does Django support NoSQL?
NoSQL basically stands for “not only SQL”. This is considered as an alternative to the traditional RDBMS or the relational Databases. Officially, Django does not support NoSQL databases. However, there are third-party projects, such as Django non-rel, that allow NoSQL functionality in Django. Currently, you can use MongoDB and Google App Engine.
27. How can you customize the functionality of the Django admin interface?
There are a number of ways to do this. You can piggyback on top of an add/ change form that is automatically generated by Django, you can add JavaScript modules using the js parameter. This parameter is basically a list of URLs that point to the JavaScript modules that are to be included in your project within a <script> tag. In case you want to do more rather than just playing around with from, you can exclusively write views for the admin.
28. Is Django better than Flask?
Django is a framework that allows you to build large projects. On the other hand, Flask is used to build smaller websites but flask is much easier to learn and use compared to Django. Django is a full-fledged framework and no third-party packages are required. Flask is more of a lightweight framework that allows you to install third-party tools as and how you like. So, the answer to this question basically depends on the user’s need and in case the need is very heavy, the answer is definitely, Django.
29. How can you limit admin access so that the objects can only be edited by those users who have created them?
Django’s ModelAdmin class provides customization hooks using which, you can control the visibility and editability of objects in the admin. To do this, you can use the get_queryset() and has_change_permission().
30. What to do when you don’t see all objects appearing on the admin site?
Inconsistent row counts are a result of missing Foreign Key values or if the Foreign Key field is set to null=False. If the ForeignKey points to a record that does not exist and if that foreign is present in the list_display method, the record will not be shown in the admin changelist.
31. What do you mean by the csrf_token?
The csrf_token is used for protection against Cross-Site Request Forgeries. This kind of attack takes place when a malicious website consists of a link, some JavaScript or a form whose aim is to perform some action on your website by using the login credentials of a genuine user.
32. Does Django support multiple-column Primary Keys?
No. Django only supports single-column Primary Keys.
33. Is it mandatory to use the model/ database layer?
No. The model/ database layer is actually decoupled from the rest of the framework.
