Essential Python Backend Interview Questions & How to Ace Them

The author, previously a C++ MFC UI developer, is now seeking Python backend positions with Django and shares interview experiences and lessons learned.

Interview experiences across several companies highlight the importance of coding daily, maintaining a GitHub portfolio, and practicing LeetCode and classic interview books.

Python syntax and fundamentals

Mutable vs immutable types

Shallow copy vs deep copy and implementing deepcopy __new__() 与 __init__() differences

Common design patterns

Encoding and decoding concepts

List comprehensions vs generators

Decorators, writing a singleton with a decorator, and differences from other singleton implementations

Regex for email validation

Garbage collection: reference counting, generational, cyclic references

Multiprocessing vs multithreading and suitability for CPU‑bound tasks

Inter‑process communication methods

Coroutines and why they can be faster than threads

range vs xrange differences

Write a C function to convert an IP string (e.g., "172.0.0.1") to a 32‑bit integer

Algorithm and sorting

Implement quicksort and heapsort; discuss algorithmic complexities

Find all combinations with spacing d in an unsorted numeric list and analyze complexity

Print all combination cases of a list

One‑line Python expression for the sum 1+2+...+10**8

Recursive palindrome check in Python

Detect a cycle in a singly linked list

Apply quicksort to a singly linked list

Estimate the median of an unsorted numeric list and state its complexity

Traverse an unknown directory using two tree‑traversal strategies

Networking basics

TCP/IP layer placement in the OSI model

Meaning of socket persistent connections

Differences between select and epoll

TCP vs UDP differences; three‑way handshake and four‑way termination

Causes of excessive TIME_WAIT states

Full HTTP request/response flow from client request to server response

GET vs POST and other HTTP methods

RESTful concepts

Common HTTP status codes such as 200, 403, 404, 504

Database fundamentals

MySQL lock types and how deadlocks occur

Reasons for and methods of sharding and partitioning

Differences among CHAR, VARCHAR, and TEXT

JOIN types; LEFT JOIN behavior when the right table has no matching rows (NULL)

Index types; B‑Tree vs hash index differences

Techniques for query optimization

Overview of NoSQL and Redis storage types

Linux and tooling

Common Linux and git commands with their purposes

How to view current processes and other useful commands beyond file operations

Django project knowledge

Briefly describe project responsibilities and challenges

Experience with Django admin and Flask source code; understanding of open‑source concepts

MVC vs MTV architecture

Cache usage

Purpose of middleware

CSRF protection in Django and XSS considerations

Design a simple login flow

Session vs cookie differences and why sessions are considered secure

Roles of uWSGI and Nginx in deployment

Conclusion: Mastering these topics and consistently uploading code to GitHub can help candidates pass junior web backend interviews. A curated GitHub repository (https://github.com/taizilongxu/interview_python) is shared for further study.