100+ Python and Django Developer Interview Questions and Answers

Entering a URL in the Chrome URL bar initiates a request to the server hosting the website.

• Chrome sends a request to the server hosting the website

• The server responds with the website's HTML, CSS, and JavaScript files

• Chrome renders the website using the received files

To fetch API data in Django from server using params dynamically.

• Use Django's HttpRequest object to access query parameters

• Extract the query parameter value using request.GET.get('querydata')

• Use the extracted value to dynamically fetch data from the server

Django uses Model-View-Controller (MVC) design pattern.

• Django follows the Model-View-Template (MVT) pattern, which is a variation of MVC.

• Model represents the data and business logic, View handles user interface and Template defines how data is presented.

• MVC separates the application into three interconnected components: Model, View, and Controller.

• Model represents the data and business logic, View handles user interface and Controller manages the flow between Model and View.

• E...read more

You can see raw SQL queries in Django by printing the queryset or using Django's logging capabilities.

• Print the queryset to see the raw SQL query: print(queryset.query)

• Use Django's logging capabilities to log SQL queries: import logging and set up logging configuration

Example code for an API implementing CRUD operations on a model using different HTTP methods

• Use Django REST framework to create API views for each HTTP method (GET, POST, PUT, DELETE)

• Define URL patterns in Django's urls.py to map to the corresponding API views

• Implement logic in the API views to interact with the model and perform CRUD operations

• Use serializers to convert model instances to JSON data and vice versa

To revert changes made in Django migrations, use the command 'python manage.py migrate <app_name> <migration_name>'.

• Use the command 'python manage.py showmigrations' to list all migrations and their names.

• Identify the migration name you want to revert (e.g., 'app_name', '0002_migration_name').

• Run the command 'python manage.py migrate <app_name> <migration_name>' to revert the specific migration.

Yes, AWS Lambda is considered serverless. To access an object in a different region, you can use S3 Cross-Region Replication or make the object public.

• AWS Lambda is a serverless computing service that allows you to run code without provisioning or managing servers.

• To access an object in a different region stored in an S3 bucket, you can use S3 Cross-Region Replication to automatically replicate objects across different AWS regions.

• Alternatively, you can make the object public...read more

SQL queries to find employees starting with 'S' and count employees in each department.

• Use SELECT statement with WHERE clause to find employees starting with 'S': SELECT name FROM employees WHERE name LIKE 'S%'

• Use GROUP BY clause with COUNT function to count employees in each department: SELECT department, COUNT(*) FROM employees GROUP BY department

Decorators in Django are used to modify the behavior of functions or methods. @login_required ensures user authentication, while @permission_required checks for specific permissions.

• Decorators are functions that wrap another function to modify its behavior.

• @login_required decorator ensures that the user is authenticated before accessing a view.

• @permission_required decorator checks if the user has specific permissions before allowing access.

• Example: @login_required def my_view...read more

I am familiar with several design patterns including MVC, Singleton, Factory, and Observer.

• MVC separates the application into Model, View, and Controller components.

• Singleton ensures only one instance of a class is created.

• Factory creates objects without specifying the exact class to be created.

• Observer allows objects to be notified of changes to a subject.

Different types of search algorithms with their time complexity

• Linear Search - O(n)

• Binary Search - O(log n)

• Depth First Search (DFS) - O(V + E)

• Breadth First Search (BFS) - O(V + E)

• A* Search - O(b^d)

• Greedy Best First Search - O(b^m)

Answering questions related to Python, Django, REST API, and MySQL joins.

• Functions in view.py file are used to handle HTTP requests and return HTTP responses.

• Yes, I have worked with REST API.

• Right join returns all the rows from the right table and matching rows from the left table.

• Left join returns all the rows from the left table and matching rows from the right table.

ViewSets provide a simple way to create CRUD APIs with less code compared to ModelSets.

• ViewSets reduce boilerplate code by providing default implementations for common actions like create, retrieve, update, and delete.

• ViewSets allow for more flexibility and customization compared to ModelSets, as they can be easily extended and customized to fit specific requirements.

• ViewSets are more concise and readable, making it easier for developers to understand and maintain the codebas...read more

Yes, Django supports multiple databases.

• Django allows defining multiple databases in settings.py

• Each database can have its own settings like engine, name, user, password, etc.

• Models can be assigned to specific databases using 'using' attribute

• Queries can be executed on specific databases using 'using' method

REST API is a set of rules and conventions for building and interacting with web services.

• REST stands for Representational State Transfer

• Methods available in REST API are GET, POST, PUT, DELETE

• GET - Used to retrieve data from a server

• POST - Used to send data to a server to create a new resource

• PUT - Used to update an existing resource on the server

• DELETE - Used to remove a resource from the server

• Example: GET request to fetch a list of users from a database

SQL Procedures are stored SQL code that can be executed on demand. Triggers are special types of stored procedures that are automatically executed when certain events occur.

• SQL Procedures are reusable blocks of SQL code that can be called by other programs or scripts.

• Triggers are special types of stored procedures that are automatically executed when specific events occur in the database.

• Triggers are commonly used for enforcing business rules, auditing changes, and maintainin...read more

Custom middleware in Django allows for processing requests and responses before reaching views.

• Custom middleware is a Python class that defines methods to process requests and responses in Django.

• To create custom middleware, define a class with methods like process_request, process_response, etc.

• Register the custom middleware in the Django settings.py file under the MIDDLEWARE key.

• Example code: class CustomMiddleware: def __init__(self, get_response): self.get_response = get_...read more

Message queues and caching systems are used to improve performance and scalability in web applications.

• Message queues help in decoupling components by allowing asynchronous communication between them.

• Caching systems store frequently accessed data in memory to reduce database load and improve response times.

• Popular message queue systems include RabbitMQ, Kafka, and Redis.

• Common caching systems include Memcached and Redis.

• Django provides built-in support for caching using the c...read more

Duck typing is a concept in Python where the type or class of an object is less important than the methods it defines.

• In duck typing, an object's suitability for a particular operation is determined by the presence of the required methods, rather than its type.

• It allows different objects to be used interchangeably if they have the same methods.

• Duck typing promotes flexibility and code reusability.

• An example of duck typing is the 'len()' function in Python, which can be used o...read more

Django supports multiple databases through its database router feature.

• Django allows defining multiple database connections in settings.py

• Use database routers to route specific models to different databases

• Example: routing user data to a separate database for better performance

Python is a high-level programming language known for its simplicity and readability.

• Python is used for web development, data analysis, artificial intelligence, and more.

• To use Python, you need to install it on your computer and write code in a text editor or an integrated development environment (IDE).

• Python code is executed line by line, and indentation is crucial for defining code blocks.

• Python has a vast standard library and a large community that provides numerous third-...read more

Find pairs of integers with least difference in an array

• Sort the array in ascending order

• Iterate through the array and find the minimum difference between adjacent elements

• Return the pairs of elements with the minimum difference

OAuth 2.0 is an authorization framework that allows third-party applications to access user data without sharing passwords.

• OAuth 2.0 is used to grant access to resources on behalf of a user.

• It uses access tokens to grant access to resources.

• OAuth 2.0 has four roles: resource owner, resource server, client, and authorization server.

• Examples of OAuth 2.0 providers include Google, Facebook, and Twitter.

Class-based views are based on classes and provide more structure and functionality, while function-based views are based on functions and are simpler and more flexible.

• Class-based views are defined as classes and inherit from Django's generic view classes, providing built-in functionality such as mixins and decorators.

• Function-based views are defined as functions and are more flexible, allowing for custom logic and control over the request-response cycle.

• Class-based views ar...read more

Factors like call duration, frequency of calls, payment history, customer service interactions can predict user churn. Logistic Regression model is best suited.

• Call duration: Longer calls may indicate higher satisfaction and lower likelihood of leaving.

• Frequency of calls: Higher frequency may indicate engagement and loyalty.

• Payment history: Timely payments may indicate commitment to the service.

• Customer service interactions: Negative interactions may lead to churn.

• Logistic Re...read more

To access APIs in Python, use libraries like requests or urllib.

• Use the requests library to make HTTP requests to APIs.

• Authenticate with APIs using tokens or keys.

• Parse JSON responses using the json library.

• Handle errors and exceptions when accessing APIs.

• Example: Using requests library to access Twitter API.

Tokens in 'C' language are the smallest unit of a program that is meaningful to the compiler.

• Tokens include keywords, identifiers, constants, strings, operators, and punctuation symbols.

• Examples of tokens in 'C' language: int, main, 5, 'hello', +, ;

Optimising MongoDB Database involves indexing, proper query optimization, sharding, and using the right data model.

• Create indexes on fields frequently used in queries to improve query performance.

• Use the explain() method to analyze and optimize query performance.

• Implement sharding to distribute data across multiple servers for scalability.

• Use the appropriate data model for your application to reduce the number of queries needed.

• Regularly monitor and optimize the database perf...read more

JWT stands for JSON Web Token. It is used for secure transmission of information between parties.

• JWT is a compact, URL-safe means of representing claims to be transferred between two parties.

• It is used for authentication and authorization purposes.

• JWT consists of three parts: header, payload, and signature.

• The header contains the algorithm used to sign the token.

• The payload contains the claims or information being transmitted.

• The signature is used to verify the integrity of t...read more

Django project directory structure organizes files and folders in a specific way.

• The project root directory contains manage.py file and project settings file.

• Apps are created inside the project directory.

• Static files are stored in a 'static' directory.

• Templates are stored in a 'templates' directory.

• Migrations are stored in a 'migrations' directory.

• Media files are stored in a 'media' directory.

• Virtual environment is created outside the project directory.

Count occurrence of items with count greater than 1 in an integer array.

• Create a dictionary to store the count of each item in the array.

• Iterate through the dictionary and count the items with count greater than 1.

• Return the count of items with count greater than 1.

An updated query in a database is used to modify existing data in the database.

• An updated query is used to change the values of one or more columns in a database table.

• It is typically used with the UPDATE statement in SQL.

• The updated query specifies the table to be updated, the columns to be modified, and the new values for those columns.

• It can also include conditions to specify which rows should be updated.

• For example, an updated query can be used to change the status of all...read more

Python is a high-level programming language known for its simplicity and readability. OOPs is a programming paradigm. List and tuple are both sequence data types in Python.

• Python is a versatile and powerful language used for web development, data analysis, artificial intelligence, and more.

• OOPs (Object-Oriented Programming) is a programming paradigm that organizes data and behavior into reusable structures called objects.

• List and tuple are both sequence data types in Python, ...read more

Maximum possible ways of climbing stairs with 1 or 2 steps at a time.

• Use dynamic programming approach

• Fibonacci sequence can be used to solve the problem

• For n stairs, the answer is fib(n+1)

• Example: for 3 stairs, answer is 3

Indexing in MongoDB improves query performance by allowing the database to quickly locate and retrieve specific documents.

• Indexes in MongoDB are similar to indexes in relational databases, allowing for efficient data retrieval.

• Types of indexes in MongoDB include single field, compound, multikey, text, hashed, and geospatial indexes.

• Single field indexes are created on a single field in a document, while compound indexes are created on multiple fields.

• Multikey indexes are used ...read more

Django follows Model-View-Controller (MVC) architecture with URL routing, views, and models.

• URL routing maps URLs to views

• Views handle HTTP requests and return HTTP responses

• Models define the database schema and interact with the database

• Templates render HTML pages using data from views

• Django ORM provides an abstraction layer for database operations

• Middleware provides hooks for modifying request/response objects

• Admin site provides a pre-built interface for managing models

• Stat...read more

range returns a list of numbers while xrange returns an iterator object.

• range creates a list of numbers from start to end with a step size of 1.

• xrange returns an iterator object that generates numbers on the fly.

• range takes more memory as it creates a list while xrange is memory efficient.

• In Python 3, range is similar to xrange in Python 2.

Multithreading involves multiple threads within the same process, while multiprocessing involves multiple processes.

• Multithreading shares the same memory space, while multiprocessing has separate memory space for each process.

• Multithreading is more lightweight and efficient for I/O-bound tasks, while multiprocessing is better for CPU-bound tasks.

• Multithreading can lead to race conditions and synchronization issues, while multiprocessing avoids these problems by using separate...read more

Method overloading is not supported in Python.

• Method overloading is the ability to define multiple methods with the same name but different parameters.

• Python does not support method overloading as it allows default arguments and variable-length arguments.

• Instead, we can use default arguments or variable-length arguments to achieve similar functionality.

Middleware, Signals, and Django Rest Framework are key components of Django framework.

• Middleware is a Django feature that allows you to process requests and responses globally.

• Signals are a way to allow certain senders to notify a set of receivers when some action has taken place.

• Django Rest Framework is a powerful and flexible toolkit for building Web APIs.

Techniques for scraping social networking sites involve using APIs, web scraping tools, and custom scripts.

• Utilize APIs provided by social networking sites for accessing data in a structured manner

• Use web scraping tools like BeautifulSoup or Scrapy to extract information from HTML pages

• Write custom scripts in Python using libraries like requests and selenium to automate the scraping process

• Respect the terms of service of the social networking site to avoid legal issues

Middleware is software that acts as a bridge between an application and its data.

• Middleware is used to handle requests and responses between the client and server.

• It can be used for authentication, caching, compression, and more.

• In Django, middleware is defined in settings.py and executed in order.

• Examples of middleware in Django include SessionMiddleware and CsrfViewMiddleware.

My perfect programming language is one that is versatile, efficient, and has a strong community support.

• Versatile - able to handle a wide range of tasks and projects

• Efficient - optimized for performance and speed

• Strong community support - active community for help and resources

• Examples: Python, JavaScript, Java

Models are the blueprints for creating database tables in Django.

• Models define the structure of the data and the relationships between them.

• They are defined in a models.py file within an app.

• They can be used to create, read, update, and delete data from the database.

• Fields in a model represent columns in the database table.

• Models can have methods to perform custom actions on the data.

Views are functions that handle HTTP requests and return HTTP responses in Django.

• Views are the heart of Django web application.

• They receive requests from clients and return responses.

• Views can be written as functions or classes.

• They can render HTML templates or return JSON data.

• Views can also handle form submissions and perform database operations.

I have strong skills in Python including data manipulation, web development, automation, and machine learning.

• Proficient in Python programming language

• Experience with data manipulation using libraries like Pandas and NumPy

• Knowledge of web development using Django framework

• Familiarity with automation tasks using Python scripts

• Basic understanding of machine learning concepts and libraries like scikit-learn

Lists are mutable, tuples are immutable in Python.

• Lists are enclosed in square brackets [], tuples in parentheses ().

• Lists can be modified (add, remove, change elements), tuples cannot be modified.

• Lists are used for collections of items that may change, tuples are used for fixed collections.

• Example: list_example = [1, 2, 3], tuple_example = (4, 5, 6)