Top Python with Django Interview Questions and Answers

1. What is Django?

Django is a high-level Python web framework designed to build secure and scalable web applications quickly. It follows the Model-View-Template (MVT) architectural pattern and includes built-in tools for authentication, database interactions, and URL routing.

2. Explain the MVT architecture in Django.

Model: Manages database structure and data.
View: Handles business logic and user requests.
Template: Manages presentation layer (HTML).
The urls.py file maps URLs to views.

3. What are Django models?

Models in Django represent database tables as Python classes. Each attribute in a model corresponds to a field in the table. Example:

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         class Book(models.Model):

         title = models.CharField(max_length=100)

5. What is Django ORM?

The Object-Relational Mapper (ORM) in Django allows interaction with the database using Python code instead of SQL queries. Example:

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           Book.objects.filter(title='Django')

6. What is the purpose of Django's settings.py?

The settings.py file contains project configurations like database setup, middleware, installed apps, and static files configuration.

7. What is a Django app?

An app is a modular component of a Django project that performs a specific function, such as managing users or blog posts. Use python manage.py startapp appname to create an app.

8. What are migrations in Django?

Migrations are Django's way of propagating changes in models to the database schema. Commands:

makemigrations: Create migration files.
migrate: Apply migrations.

9. What is Django's manage.py file?

manage.py is a command-line tool for performing administrative tasks like starting the server, applying migrations, and creating superusers.

10. Explain Django middleware.

Middleware is a layer between the request and response cycle. It processes requests before the view and responses before sending them back to the client.

11. What is the difference between null=True and blank=True?

null=True: Allows NULL values in the database.
blank=True: Allows form validation to accept empty values.

12. What is Django's urlpatterns?

urlpatterns is a list in urls.py that maps URLs to view functions or class-based views.

13. Explain Django's @login_required decorator.

This decorator restricts access to a view to authenticated users. Example:

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@login_required

def dashboard(request):

    return render(request, 'dashboard.html')

14. What is the difference between render() and redirect()?

render(): Renders a template with context.
redirect(): Redirects to a different URL.

15. What are Django signals?

Signals allow decoupled components to communicate. Example: pre_save, post_save.

16. What is django.contrib.auth?

This is Django's built-in authentication system for managing users, permissions, and groups.

17. How do you handle static files in Django?

Static files (CSS, JS, images) are managed using the STATICFILES_DIRS and STATIC_URL settings.

18. What is a QuerySet?

A QuerySet represents a collection of database queries. Example:

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Book.objects.all()

19. Explain Django's caching mechanism.

Django supports caching to optimize performance. Supported backends include Memcached, Redis, and local memory caching.

20. What are class-based views?

Class-based views organize views into classes rather than functions, offering better code reuse.

21. What is the difference between get() and filter()?

get(): Returns a single object.
filter(): Returns a QuerySet.

22. Explain Django's forms.py.

The forms.py file handles form creation and validation. Example:

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from django import forms

class BookForm(forms.Form):

    title = forms.CharField(max_length=100)

23. What are Django REST Framework (DRF) serializers?

Serializers convert complex data types into JSON. Example:

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from rest_framework import serializers

class BookSerializer(serializers.ModelSerializer):

    class Meta:

        model = Book

24. What are migrations?

Migrations make schema changes to the database using Python code instead of raw SQL

25. What is the difference between ForeignKey and OneToOneField?

ForeignKey: Many-to-one relationship.
OneToOneField: One-to-one relationship.

26. What is Django's csrf_token?

csrf_token protects against Cross-Site Request Forgery attacks by adding a token to forms.

27.What is Django's URLConf?

URLConf maps URLs to view functions or classes.

28. How do you create a superuser?

Run:

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python manage.py createsuperuser

29. What is Django's reverse() function?

reverse() generates URLs dynamically based on view names.

30. What is the difference between AutoField and UUIDField?

AutoField: Auto-incrementing integer field.
UUIDField: Field for storing universally unique identifiers.

31. What is Django’s get_object_or_404()?

It fetches an object from the database and raises an Http404 exception if the object doesn’t exist. Example:

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from django.shortcuts import get_object_or_404  

book = get_object_or_404(Book, id=1)

32. Explain the difference between on_delete=models.CASCADE and on_delete=models.SET_NULL.

CASCADE: Deletes related objects when the referenced object is deleted.
SET_NULL: Sets the foreign key to NULL when the referenced object is deleted.

33. What are Django generic views?

Generic views are pre-built views for common tasks like displaying lists or detail pages. Example: ListView, DetailView.

34. Explain Django middleware with an example.

Middleware processes requests and responses globally. Example: SessionMiddleware handles user sessions.

35. What is Django’s Paginator class?

It divides querysets into smaller chunks for pagination. Example:

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from django.core.paginator import Paginator  

p = Paginator(Book.objects.all(), 10)

36. What are Django fixtures?

Fixtures are serialized data used to populate the database. Example: JSON or XML files loaded via loaddata.

37. What is Django’s AUTH_USER_MODEL?

It defines the custom user model in Django projects using settings.AUTH_USER_MODEL.

38. How do you reset migrations in Django?

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python manage.py flush  

python manage.py makemigrations  

python manage.py migrate

39. What is Django's SlugField?

A SlugField creates SEO-friendly URLs by converting text into URL-safe slugs. Example:

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slug = models.SlugField(unique=True)

40. Explain Django's ManyToManyField.

It defines a many-to-many relationship between two models. Example:

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authors = models.ManyToManyField(Author)

41. What are context processors in Django?

They pass additional context to templates globally. Example: request, user, or custom variables.

42. How do you customize the Django admin interface?

By overriding admin.py and using methods like list_display and search_fields.

43. Explain Django's pre_save and post_save signals.

pre_save: Triggered before saving an object.
post_save: Triggered after saving an object.

44. What is Django's JsonResponse?

It returns JSON data from a Django view. Example:

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from django.http import JsonResponse  

return JsonResponse({'message': 'Hello, World'})

45. What is Django’s StaticRoot?

STATIC_ROOT is the directory where static files are collected using collectstatic.

46. What is MEDIA_ROOT?

MEDIA_ROOT is the directory where user-uploaded files are stored.

47. What is the difference between STATIC_URL and MEDIA_URL?

STATIC_URL: URL for static files.
MEDIA_URL: URL for user-uploaded files.

48. What is Django's caching framework?

It improves performance by temporarily storing data. Supported backends include Redis and Memcached.

49. What are Django’s template filters?

They transform variables in templates. Example: {{ name|upper }} converts text to uppercase.

50. How do you manage database connections in Django?

Using DATABASES in settings.py.

51. What is Django’s ALLOWED_HOSTS?

It specifies valid domain names or IP addresses to prevent HTTP Host header attacks.

52. What is the difference between DEBUG=True and DEBUG=False?

DEBUG=True: Displays detailed error messages.
DEBUG=False: Hides errors and logs them.

53. What are Django sessions?

Sessions store user-specific data on the server side.

54. What is the difference between @staticmethod and @classmethod in views?

@staticmethod: Does not access class or instance attributes.
@classmethod: Works with class-level attributes.

55. Explain Django’s file upload handling.

Django handles file uploads using FileField and MEDIA_ROOT.

56. What is Django’s TemplateView?

A class-based view for rendering templates. Example:

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from django.views.generic import TemplateView  

class HomeView(TemplateView):  

    template_name = 'home.html'

57. What are signals in Django?

Signals are used for event-driven programming between decoupled components.

58. Explain csrf_exempt.

It disables CSRF protection for specific views. Example:

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from django.views.decorators.csrf import csrf_exempt  

@csrf_exempt  

def my_view(request):  

    pass

59. What is Django's @property decorator?

It allows a method to act as an attribute.

60. How do you secure a Django app?

Use ALLOWED_HOSTS.
Enable HTTPS.
Protect against SQL injection and CSRF.

61. What are Django REST Framework views?

Views handle HTTP requests and responses. Examples: APIView, ViewSet.

62. What are Django mixins?

Mixins are reusable view logic components.

63. What is Django’s @api_view decorator?

It converts a function-based view into an API view.

64. Explain Django’s throttling.

It limits the number of API requests a user can make.

65. What are the security best practices in Django?

Enable SECURE_SSL_REDIRECT.
Use strong passwords.
Regularly update Django.

66. What is Django's WSGI?

WSGI is the Python Web Server Gateway Interface, acting as an interface between web servers and Django.

67. What is ASGI?

ASGI is the Asynchronous Server Gateway Interface for handling async requests.

68. Explain Django's select_related() and prefetch_related().

select_related: Optimizes queries for ForeignKey fields.
prefetch_related: Optimizes queries for ManyToMany fields.

69. What is Django's default database?

SQLite is the default database in Django.

70. Explain the collectstatic command.

It gathers static files into a single directory.

71. What is the role of the MapReduce framework in Hadoop?

The MapReduce framework is the engine that processes the data in Hadoop. It consists of two main phases:

Map phase: The input data is processed in parallel by multiple Mappers.
Reduce phase: The intermediate results from Mappers are combined and processed by Reducers to generate the final output.

72. What are the advantages of using Hadoop for big data?

Scalability: Hadoop can scale out horizontally by adding more nodes to the cluster.
Fault tolerance: Data is replicated across nodes, ensuring data availability even in case of node failures.
Cost-effective: Hadoop runs on commodity hardware, reducing infrastructure costs.
Flexibility: It can handle both structured and unstructured data.

73. What is Hadoop Distributed Cache and how does it work?

The Hadoop Distributed Cache is a mechanism that distributes files (such as configuration files, libraries, or archives) across the cluster for use by MapReduce tasks. It allows tasks to access these files locally without requiring network calls.

74. What is a block in HDFS and what is its default size?

A block in HDFS is the smallest unit of storage in the system. The default block size in HDFS is 128 MB, but it can be configured based on the needs of the application.

75. What is the difference between Hadoop and Spark?

Hadoop is primarily a batch processing system, whereas Spark provides both batch and real-time processing capabilities.
Spark is faster than Hadoop due to its in-memory computation, while Hadoop uses disk-based storage for intermediate data.
Spark also supports advanced analytics like machine learning and graph processing.

76. What is the role of the Hadoop client?

The Hadoop client is an interface through which users interact with the Hadoop cluster. It allows for submitting jobs, querying data in HDFS, and performing other administrative tasks.

77. What is the difference between an HDFS block and a disk block?

An HDFS block is a logical division of data in HDFS, typically 128 MB in size. It is distributed across multiple nodes for fault tolerance and scalability.
A disk block is the smallest unit of data on a physical disk, and its size is typically much smaller than an HDFS block.

79. How does HDFS provide fault tolerance?

HDFS provides fault tolerance by replicating data blocks across multiple nodes. If one node or DataNode fails, the data can still be accessed from other replicas. The default replication factor is 3.

80. What is the purpose of the Hadoop Distributed FileSystem (HDFS)?

The purpose of HDFS is to store large datasets across multiple nodes in a Hadoop cluster. It ensures high availability, reliability, and scalability of data storage.

81. What is the function of the NodeManager in YARN?

The Node Manager is responsible for managing the individual nodes in the cluster. It monitors resource usage, enforces resource limits, and reports node health to the ResourceManager.

82. What is a job tracker in Hadoop 1.x?

In Hadoop 1.x, the JobTracker was responsible for managing the scheduling and execution of MapReduce jobs. It handled job execution, task tracking, and failure management.

83. What are the key differences between Hadoop and traditional RDBMS systems?

Hadoop is designed for distributed processing and can handle both structured and unstructured data, whereas traditional RDBMS systems are designed for structured data and run on a single server.
Hadoop scales horizontally by adding more nodes, while RDBMS systems typically scale vertically by upgrading hardware.
Hadoop is fault-tolerant and supports parallel processing, while RDBMS systems typically offer limited parallelism and no native fault tolerance.

84. What is the role of the ResourceManager in Hadoop YARN?

The ResourceManager is responsible for managing the resources of the entire cluster. It schedules jobs, allocates resources, and ensures that applications get the resources they need to run efficiently.

85. What is the Hadoop Streaming API?

The Hadoop Streaming API allows developers to write MapReduce programs in languages like Python, Ruby, or Perl. It lets users use custom mappers and reducers without needing to write Java code.

86. How does MapReduce process data?

MapReduce processes data by dividing it into two phases:

Map phase: Input data is split into smaller chunks and processed in parallel by multiple Mappers.
Reduce phase: The intermediate data from the Mappers is grouped by key and processed by the Reducers to generate the final result.

87. What is the difference between a mapper and a reducer in Hadoop MapReduce?

A mapper processes input data and produces intermediate key-value pairs.
A reducer takes the output from the mapper, processes it by combining values with the same key, and produces the final output.

88. What is the significance of HBase in the Hadoop ecosystem?

HBase is a NoSQL database that is built on top of Hadoop and provides real-time read/write access to large datasets. It is designed for applications requiring random, low-latency access to data.

89. What is the Hadoop ecosystem?

The Hadoop ecosystem consists of various tools and frameworks that complement the core Hadoop system. These include Hive (SQL-based querying), Pig (data flow language), HBase (NoSQL database), and Oozie (workflow scheduler).

90. What is a sequence file in Hadoop?

A sequence file is a binary format that stores data in the form of key-value pairs. It is often used to store data for MapReduce jobs because it is more efficient than plain text files.

91. What is the difference between structured, semi-structured, and unstructured data?

Structured data refers to data that is organized in a predefined format (e.g., relational databases).
Semi-structured data refers to data that doesn't have a rigid structure but contains tags or markers to separate elements (e.g., XML or JSON).
Unstructured data refers to data that has no defined format or structure (e.g., images, videos, text).

92. What is the purpose of the Hadoop Common module?

The Hadoop Common module contains the Java libraries and utilities required by other modules in the Hadoop ecosystem. It provides essential functions for data serialization, file system management, and job execution.

93. What is a combiner in Hadoop?

A combiner is an optional optimization in Hadoop that performs partial aggregation of the data in the Mapper before it is sent to the Reducer. This helps reduce the amount of data transferred between the Map and Reduce tasks.

94. How is a job submitted in Hadoop?

A job is submitted to Hadoop via the Hadoop client. The client uses the JobClient class to submit the job, and the job is executed on the cluster using the available resources managed by the ResourceManager.

95. What is the difference between Hive and Pig in Hadoop?

Hive is a data warehousing tool that allows SQL-like querying on data stored in Hadoop.
Pig is a data flow language designed for processing and analyzing large datasets, often used for ETL (Extract, Transform, Load) operations.

96. What is the role of Zookeeper in the Hadoop ecosystem?

Zookeeper is a distributed coordination service used to maintain configuration information, provide synchronization, and manage the naming of services in distributed systems. It is crucial for systems like HBase and Kafka.

97. What are the limitations of Hadoop?

Hadoop is primarily optimized for batch processing and may not be suitable for real-time data processing.
It requires a significant amount of storage and computing resources.
It has a high learning curve for new users and administrators.

98. What is the significance of data replication in HDFS?

Data replication in HDFS ensures high availability and fault tolerance. If a DataNode fails, the system can retrieve the data from other replicas stored across different nodes, minimizing data loss.

99. What is the default number of replications in HDFS?

The default replication factor in HDFS is 3, meaning each data block is replicated three times across different DataNodes in the cluster.

100. What is a task tracker in Hadoop 1.x?

A TaskTracker is a daemon in Hadoop 1.x responsible for executing the tasks assigned by the JobTracker. It monitors the task's progress and reports back to the JobTracker.