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Python Interview Questions

Questionnaire for 5 year candidate

🐍 Python Software Engineer – Evaluation Questionnaire

✅ Section 1: Core Python Knowledge

  1. Explain Python’s memory management model. How does garbage collection work?
  2. What are decorators and how do they work? Provide a real-world use case.
  3. Describe the difference between @staticmethod, @classmethod, and instance methods.
  4. What is a generator? How does it differ from a regular function?
  5. Explain Python’s GIL (Global Interpreter Lock). How does it impact multi-threaded applications?
  6. When would you use __slots__ in a Python class?
  7. What are context managers? How does the with statement work internally?
  8. Explain list comprehensions vs. generator expressions. When would you prefer one over the other?

✅ Section 2: Advanced Python & Libraries

  1. How would you handle concurrency in Python? Compare threading, multiprocessing, and async programming.
  2. Given a large CSV file (5GB+), how would you process it efficiently in Python?
  3. What are the differences between deepcopy() and copy()?
  4. Have you used Pandas or NumPy? Share a case where these libraries helped optimize performance.
  5. Explain how you would structure a Python package for a large-scale project.
  6. How do you manage dependencies and virtual environments in Python?

✅ Section 3: System Design & Architecture

  1. Design a RESTful API for a library management system.
    • Outline the architecture, endpoints, and data model.
    • Consider authentication and rate-limiting.
  2. How would you scale a Python web application to handle 10,000 concurrent users?
  3. What design patterns have you used in past projects? Share real-world examples.
  4. Explain the difference between monolithic and microservices architectures. When would you choose one over the other?
  5. Discuss the trade-offs between using SQL (PostgreSQL) vs. NoSQL (MongoDB) in a Python project.

✅ Section 4: Cloud, DevOps & Databases

  1. Which cloud platforms (AWS, Azure, GCP) have you worked with? Describe a Python project you deployed on the cloud.
  2. How would you implement CI/CD for a Python microservice?
  3. Have you worked with Docker or Kubernetes? How did they help in your project?
  4. What steps would you take to ensure security in a Python-based API (e.g., JWT, OAuth2)?
  5. Explain how message queues (e.g., RabbitMQ, SQS) can improve a Python application’s scalability.
  6. What are common performance bottlenecks in Python web applications, and how would you fix them?

✅ Section 5: Problem-Solving (Coding Challenge)

  1. Write a Python function that identifies duplicates in a large dataset and removes them while maintaining order.
  2. Given a list of API endpoints, write an asynchronous Python script to fetch data from all endpoints and combine the results.
  3. Implement a caching layer in Python using Redis for an API that fetches weather data.
  4. Write SQL queries for the following:
    • Find the second highest salary in a table.
    • List all customers who haven’t placed an order in the last 6 months.
  5. (Optional - Debugging Task): Provide a buggy code snippet and ask the candidate to debug and fix it live.

✅ Section 6: Soft Skills & Behavioral Questions

  1. How do you approach code reviews? What’s your strategy for giving constructive feedback?
  2. Describe a time when you faced a major roadblock in a project. How did you overcome it?
  3. Have you mentored junior developers? Share your approach.
  4. How do you stay updated with new Python libraries, frameworks, and best practices?
  5. Tell me about a project where you had to collaborate with cross-functional teams.

📊 Evaluation Rubric:

Category Weight Rating (1-5) Comments
Core Python Knowledge 20%    
System Design 20%    
Problem-Solving 20%    
Cloud/DevOps (if needed) 15%    
Database Expertise 10%    
Soft Skills 15%    

✅ Section 7: SQL & Database Design

📊 Basic SQL Queries

  1. Write a query to retrieve the top 5 highest-paid employees from an employees table.
  2. Find the total number of orders placed in the last month from an orders table.
  3. How would you select all customers who haven’t placed any orders? (Use LEFT JOIN or NOT EXISTS)
  4. Explain the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN.
  5. What is the difference between WHERE and HAVING clauses?

📊 Intermediate SQL Concepts

  1. Given a table sales (id, product_id, quantity, sale_date), write a query to find the best-selling product for each month.
  2. What’s the difference between RANK(), DENSE_RANK(), and ROW_NUMBER()? Provide examples.
  3. Write a query to find duplicate records in a table and remove them.
  4. How would you calculate the cumulative sales for each product ordered by sale date? (Use window functions)
  5. Explain the concept of indexing. When would you avoid using an index?

📊 Advanced SQL & Optimization

  1. How would you optimize a slow-running query fetching millions of rows? (Discuss indexing, query plans, etc.)
  2. What’s the difference between UNION and UNION ALL? When would you use one over the other?
  3. Explain ACID properties in relational databases. Why are they important?
  4. Design a normalized schema for an e-commerce platform. (Cover customers, products, orders, and payments)
  5. How would you handle schema migrations in a production environment?

📊 SQL Problem-Solving Challenges

  1. Given tables orders(order_id, customer_id, amount, order_date) and customers(customer_id, name):
    • Find customers who have placed orders worth more than $5000.
    • List customers who placed orders in January 2024 but not in February 2024.
  2. Write a query to find the second highest salary from an employees table. (Without using LIMIT or OFFSET)
  3. How would you pivot a table in SQL to display monthly sales for each product as columns? (Use CASE WHEN or PIVOT if supported)
  4. Create a recursive CTE to find the hierarchical structure of employees reporting to a specific manager.
  5. Given a large transaction table, how would you identify anomalies or suspicious transactions? (Discuss window functions or data mining techniques)