Django along with Python is one of the most in-demand skills and surely amongst some of the trickiest ones. So if you want to prepare yourself to perform the best in the upcoming Django interview, here are the top 50 commonly asked Django Interview Questions and Answers.
|Project Type||Supports large projects||Built for smaller projects|
|Templates, Admin and ORM||Built-in||Requires installation|
|Ease of Learning||Requires more learning and practice||Easy to learn|
|Flexibility||Allows complete web development without the need for third-party tools||More flexible as the user can select any third-party tools according to their choice and requirements|
|Visual Debugging||Does not support Visual Debug||Supports Visual Debug|
|Type of framework||Batteries included||Simple, lightweight|
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.
Some of the companies that make use of Django are Instagram, DISCUS, Mozilla Firefox, YouTube, Pinterest, Reddit, etc.
To check for the version of Django installed on your system, you can open the command prompt and enter the following command:
You can also try to import Django and use the get_version() method as follows:
import django print(django.get_version())
Django follows the MVT or Model View Template architecture which is based on the MVC or Model View Controller architecture. The main difference between these two is that Django itself takes care of the controller part.
According to Django, the ‘view’ basically describes the data presented to the user. It does not deal with how the data looks but rather what the data actually is. Views are basically callback functions for the specified URL’s and these callback functions describe which data is presented.
The ‘templates’ on the other hand deal with the presentation of data, thereby, separating the content from its presentation. In Django, views delegate to the templates to present the data.
The ‘controller’ here is Django itself which sends the request to the appropriate view in accordance with the specified URL. This is why Django is referred to as MTV rather than MVC architecture.
django-admin is the command-line utility of Django for administrative tasks. Using the django-admin you can perform a number of tasks some of which are listed out in the following table:
To display the usage information and the list of the commands provided by each application
To display the list of available commands
django-admin help –command
To display the description of a given command and the list of its available options
django-admin help <command>
Determining the version of Django
Creating new migrations based on the changes made in models
Synchronizing the database state with the current set of models and migrations
Starting the development server
Sending a test email in order to confirm the email sending through Django is working
To start the Python interactive interpreter
To show all the migrations in your project
Django comes with a default database which is SQLite. To connect your project to this database, use the following commands:
When you create a project using the startproject command, the following files will be created:
A command-line utility that allows you to interact with your Django project
An empty file that tells Python that the current directory should be considered as a Python package
Consists of the settings for the current project
Contains the URL’s for the current project
This is an entry-point for the web servers to serve the project you have created
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.
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.
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.
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 ‘n’ number of apps and a single app can be in multiple projects.
Django has three possible inheritance styles:
Abstract base classes
Used when you want to use the parent class to hold information that you don’t want to type for each child model. Here, the parent class is never used in solitude
Used when you have to subclass an existing model and want each
model to have its own database table
Used if you only want to modify the Python-level behavior of a model, without changing the ‘models’ fields in any way
Django consists of a signal dispatcher that helps allow decoupled applications to get notified when actions occur elsewhere in the framework. Django provides a set of built-in signals that basically allow senders to notify a set of receivers when some action is executed. Some of the signals are as follows:
Sent before or after a model’s save() method is called
Sent before or after a model’s delete() method or queryset’s delete() method is called
Sent when Django starts or finishes an HTTP request
‘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 from_db_value() method_._ Therefore, fields are fundamental pieces in different Django APIs such as models and querysets.
To create a Django project, cd into the directory where you would like to create your project and type the following command:
NOTE: Here, xyz is the name of the project. You can give any name that you desire.
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.
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.
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.
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.
Caching basically means to save the output of an expensive calculation in order to avoid performing the same calculation again. Django provides a robust cache system which in turn helps you save dynamic web pages so that they don’t have to be evaluated over and over again for each request. Some of the caching strategies of Django are listed down in the following table:
Memory-based cache server which is the fastest and most efficient
Cache values are stored as separate files in a serialized order
This is actually the default cache in case you have not specified any other. This type of cache is per-process and thread-safe as well
Cache data will be stored in the database and works very well if you have a fast and well-indexed database server
Middleware is a framework that is 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.
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.
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.
In order to view all the items from your database, you can make use of the ‘all()’ function in your interactive shell as follows:
To filter out some element from your database, you either use the get() method or the filter method as follows:
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 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.
In order to make use of file-based sessions, you will need to set the SESSION_ENGINE setting to “django.contrib.sessions.backends.
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. For more details about this, you can refer to the answer to Q29.
Django uses its own exceptions as well as those present in Python. Django core exceptions are present in django.core.exceptions class some of which are mentioned in the table below:
Raised when you try to use your models before the app loading process (initializes the ORM) is completed.
This is the base class for DoesNotExist exceptions
This exception may be raised if a query won’t return any result
This exception is raised by a model’s _meta.get_field() function in case the requested field does not exist
This is raised by a query if multiple objects are returned and only one object was expected
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.
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 it. 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.
Django is not a CMS (content-management-system) . It is just a Web framework, a tool that allows you to build websites.
The following table gives you the details of the versions of Python that you can use for Django:
Python 3 is actually the most recommended because it is fast, has more features and is better supported. In the case of Python 2.7, Django 1.1 can be used along with it but only till the year 2020.
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.
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.
A view in Django either returns an HttpResponse or raises an exception such as Http404. HttpResponse contains the objects that consist of the content that is to be rendered to the user.
from django.http import HttpResponse def hello_world(request): html = " <h1>Hello World!</h1> " return HttpResponse(html)
Q42. What should be done in case you get a message saying “Please enter the correct username and password” even after entering the right details to log in to the admin section?
In case you have entered the right details and still not able to login to the admin site, cross verify if the user account has is_active and is_staff attributes set to True. The admin site allows only those users for whom these values are set to True.
In this case, the login cookie is not being set rightly. This happens if the domain of the cookie sent out by Django does not match the domain in your browser. For this, you must change the SESSION_COOKIE_DOMAIN setting to match that of your browser.
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().
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 the admin changelist.
No. Django only supports single-column Primary Keys.
First, make sure that your DEBUG setting is set to True. Then, type the following commands:
from django.db import connection connection.queries
No. The model/ database layer is actually decoupled from the rest of the framework.
You can make use of the RequestContext in case all your templates require the same objects, such as, in the case of menus. This method takes an HttpRequest as its first parameter and it automatically populates the context with a few variables, according to the engine’s
context_processors configuration option.
Android Interview Questions and Answers from Beginner to Advanced level
DataFlair is committed to provide you all the resources to make you an android professional. We started with android tutorials along with practicals, then we published Real-time android projects along with source code. Now, we come up with frequently asked android interview questions, which will help you in showing expertise in your next interview.
Android – one of the hottest technologies, which is having a bright future. Get ready to crack your next interview with the following android interview questions. These interview questions start with basic and cover deep concepts along with advanced topics.
1. What is Android?
Android is an open-source mobile operating system that is based on the modified versions of Linux kernel. Though it was mainly designed for smartphones, now it is being used for Tablets, Televisions, Smartwatches, and other Android wearables.
2. Who is the inventor of Android Technology?
The inventors of Android Technology are- Andry Rubin, Nick Sears, and Rich Miner.
3. What is the latest version of Android?
The latest version of Android is Android 10.0, known as Android Q. The upcoming major Android release is Android 11, which is the 18th version of Android. [Note: Keep checking the versions, it is as of June 2020.]
4. How many Android versions can you recall right now?
Till now, there are 17 versions of Android, which have their names in alphabetical order. The 18th version of Android is also going to come later this year. The versions of Android are here:
5. Explain the Android Architecture with its components.
This is a popular android developer interview question
Android Architecture consists of 5 components that are-
a. Linux Kernel: It is the foundation of the Android Architecture that resides at the lowest level. It provides the level of abstraction for hardware devices and upper layer components. Linux Kernel also provides various important hardware drivers that act as software interfaces for hardwares like camera, bluetooth, etc.
b. Native Libraries: These are the libraries for Android that are written in C/C++. These libraries are useful to build many core services like ART and HAL. It provides support for core features.
c. Android Runtime: It is an Android Runtime Environment. Android Operating System uses it during the execution of the app. It performs the translation of the application bytecode into the native instructions. The runtime environment of the device then executes these native instructions.
d. Application Framework: Application Framework provides many java classes and interfaces for app development. And it also provides various high-level services. This complete Application framework makes use of Java.
e. Applications: This is the topmost layer of Android Architecture. It provides applications for the end-user, so they can use the android device and compute the tasks.
6. What are the services that the Application framework provides?
The Android application framework has the following key services-
a. Activity Manager: It uses testing and debugging methods.
b. Content provider: It provides the data from application to other layers.
c. Resource Manager: This provides users access to resources.
d. Notification Manager: This gives notification to the users regarding actions taking place in the background.
e. View System: It is the base class for widgets, and it is also responsible for event handling.
7. What are the important features of Linux Kernel?
The important features of the Linux Kernel are as follows:
a. Power Management: Linux Kernel does power management to enhance and improve the battery life of the device.
b. Memory Management: It is useful for the maximum utilization of the available memory of the device.
c. Device Management: It includes managing all the hardware device drivers. It maximizes the utilization of the available resources.
d. Security: It ensures that no application has any such permission that it affects any other application in order to maintain security.
e. Multi-tasking: Multi-tasking provides the users the ease of doing multiple tasks at the same time.
8. What are the building blocks of an Android Application?
This is a popular android interview question for freshers.
The main components of any Android application are- Activity, Services, Content Provider, and Broadcast Receiver. You can understand them as follows:
a. Activity- It is a class that acts as the entry point representing a single screen to the user. It is like a window to show the user interface.
b. Services- Services are the longest-running component that runs in the background.
c. Content Provider- The content provider is an essential component that allows apps to share data between themselves.
d. Broadcast receivers- Broadcast receiver is another most crucial application component. It helps the apps to receive and respond to broadcast messages from the system or some other application.
9. What are the important components of Android Application?
The Components of Android application are listed below:
10. What are the widgets?
Widgets are the variations of Broadcast receivers. They are an important part of home screen customization. They often display some data and also allow users to perform actions on them. Mostly they display the app icon on the screen.
11. Can you name some types of widgets?
Mentioned below are the types of widgets-
a. Informative Widgets: These widgets show some important information. Like, the clock widget or a weather widget.
b. Collective Widgets: They are the collection of some types of elements. For example, a music widget that lets us change, skip, or forward the song.
c. Control Widgets: These widgets help us control the actions within the application through it. Like an email widget that helps check the recent mails.
d. Hybrid Widgets: Hybrid widgets are those that consist of at least two or more types of widgets.
12. What are Intents?
Intents are an important part of Android Applications. They enable communication between components of the same application as well as separate applications. The Intent signals the Android system about a certain event that has occurred.
13. Explain the types of intents briefly?
Intent is of three types that are-
a. Implicit Intents: Implicit intents are those in which there is no description of the component name but only the action.
b. Explicit Intents: In explicit intents, the target component is present by declaring the name of the component.
c. Pending Intents: These are those intents that act as a shield over the Intent objects. It covers the intent objects and grants permission to the external app components to access them.
14. What is a View?
A view is an important building block that helps in designing the user interface of the application. It can be a rectangular box or a circular shape, for example, Text View, Edit Text, Buttons, etc. Views occupy a certain area of the screen, and it is also responsible for event handling. A view is the superclass of all the graphical user interface components.
15. What do you understand by View Group?
It is the subclass of the ViewClass. It gives an invisible container to hold layouts or views. You can understand view groups as special views that are capable of holding other views, that are Child View.
16. What do you understand about Shared Preferences?
It is a simple mechanism for data storage in Android. In this, there is no need to create files, and using APIs, it stores the data in XML files. It stores the data in the pair of key-values. SharedPreferences class lets the user save the values and retrieve them when required. Using SharedPreferences we can save primitive data like- boolean, float, integer, string and long.
17. What is a Notification?
A notification is just like a message that shows up outside the Application UI to provide reminders to the users. They remind the user about a message received, or some other timely information from the app.
18. Give names of Notification types.
There are three types of notifications namely-
a. Toast Notification- This notification is the one that fades away sometime after it pops up.
b. Status Notification- This notification stays till the user takes some action on it.
c. Dialog Notification- This notification is the result of an Active Activity.
19. What are fragments?
A fragment is a part of the complete user interface. These are present in Activity, and an activity can have one or more fragments at the same time. We can reuse a fragment in multiple activities as well.
20. What are the types of fragments?
There are three types of fragments that are: Single Fragment, List Fragment, Fragment Transactions.
21. What are Layout XML files?
Layout XML files contain the structure for the user interface of the application. The XML file also contains various different layouts and views, and they also specify various GUI components that are there in Activity or fragments.
22. What are Resources in Android Application?
The resources in Android Apps defines images, texts, strings, colors, etc. Everything in resources directory is referenced in the source code of the app so that we can use them.
23. Can you develop Android Apps with languages other than Java? If so, name some.
Yes, there are many languages that we can work with, for the development of Android Applications. To name some, I would say Java, Python, C, C++, Kotlin, C#, Corona/LUA.
24. What are the states of the Activity Lifecycle?
Activity lifecycle has the following four stages-
a. Running State: As soon as the activity starts, it is the first state.
b. Paused State: When some other activity starts without closing the previous one, the running activity turns into the Paused state.
c. Resume State: When the activity opens again after being in pause state, it comes into the Resume State.
d. Stopped State: When the user closes the application or stops using it, the activity goes to the Stopped state.
25. What are some methods of Activity?
The methods of Activity are as follows:
26. How can you launch an activity in Android?
We launch an activity using Intents. For this we need to use intent as follows:
27. What is the service lifecycle?
There are two states of a service that are-
a. Started State: This is when the service starts its execution. A Services come in start state only through the startService() method.
b. Bounded State: A service is in the bounded state when it calls the method bindService().
28. What are some methods of Services?
The methods of service are as follows-
29. What are the types of Broadcast?
Broadcasts are of two types that are-
a. Ordered Broadcast: Ordered broadcasts are Synchronous and work in a proper order. It decides the order by using the priority assigned to the broadcasts.
b. Normal Broadcast: These are asynchronous and unordered. They are more efficient as they run unorderly and all at once. But, they lack full utilization of the results.
30. What are useful impotent folders in Android?
The impotent folders in an Android application are-
31. What are the important files for Android Application when working on Android Studio?
This is an important android studio interview question
There are following three files that we need to work on for an application to work-
a. The AndroidManifest.xml file: It has all the information about the application.
b. The MainActivity.java file: It is the app file that actually gets converted to the dalvik executable and runs the application. It is written in java.
c. The Activity_main.xml file: It is the layout file that is available in the res/layout directory. It is another mostly used file while developing the application.
32. Which database do you use for Android Application development?
The database that we use for Android Applications is SQLite. It is because SQLite is lightweight and specially developed for Android Apps. SQLite works the same way as SQL using the same commands.
33. Tell us some features of Android OS.
The best features of Android include-
34. Why did you learn Android development?
Learning Android Studio is a good idea because of the following-
35. What are the different ways of storage supported in Android?
The various storage ways supported in Android are as follows:
36. What are layouts?
Layout is nothing but arrangements of elements on the device screen. These elements can be images, tests, videos, anything. They basically define the structure of the Android user interface to make it user friendly.
37. How many layout types are there?
The type of layouts used in Android Apps are as follows:
38. What is an APK?
An APK stands for Android Package that is a file format of Android Applications. Android OS uses this package for the distribution and installation of the Android Application.
39. What is an Android Manifest file?
The manifest file describes all the essential information about the project application for build tools, Android operating system, and google play. This file is a must for every Android project that we develop, and it is present in the root of the project source set.
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Here is a list of 50 interview questions with answers. The list is in no particular order.
I hope you enjoy it.
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Developers worldwide use C++ to build systems software, database software, embedded software, enterprise applications, GUI-based applications, compilers, advanced computation & graphics, operating systems, browsers, games, cloud systems, etc. Naturally, C++ is still a highly relevant programming language.
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