Essential Python Backend Interview Questions and How to Ace Them

The author, originally a C++ MFC UI developer at a state‑owned research institute, is now seeking a Python backend position using Django and shares his interview experiences to help others prepare.

He interviewed at several companies (two Beijing startups, Guokr, Zhihu, iQiyi, NetEase in Hangzhou) and stresses that consistent daily coding and uploading work to GitHub dramatically improves interview prospects.

He also notes the importance of a well‑rounded skill set, citing the "wooden bucket" principle: neglecting any area (e.g., algorithms, system design) can cause failure.

Python Syntax and Fundamentals

Mutable vs immutable types

Shallow copy vs deep copy; implementing deepcopy __new__() vs __init__() differences

Common design patterns

Encoding/decoding concepts

List comprehensions vs generators

Decorators and implementing a singleton with a decorator

Regex for email validation

Garbage collection: reference counting, generational, cyclic references

Multiprocessing vs multithreading; CPU‑bound tasks

Inter‑process communication methods

Coroutines and why they can be faster than threads

range vs xrange (Python 2 vs 3)

Write a C function that converts an IP string (e.g., "172.0.0.1") to a 32‑bit binary number

Algorithm and Sorting

Implement quicksort and heap sort; discuss their time complexities and worst‑case optimizations for quicksort

Given an unsorted numeric list of length n, find all combinations with a fixed interval d and state the algorithm’s complexity

Print all possible combinations of a list A = [A1, A2, …, An]

One‑line Python expression to compute 1+2+…+10**8

Recursive palindrome check for a string

Detect a cycle in a singly linked list of unknown length

Apply quicksort to a singly linked list

Estimate the median of an unsorted numeric list and give the algorithm’s complexity

Traverse an unknown directory tree using both depth‑first and breadth‑first strategies

Network Fundamentals

Identify which OSI layer TCP and IP belong to

Explain long‑lived socket connections

Differences between select and epoll

TCP vs UDP differences; describe the 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

Understanding of RESTful principles

Common HTTP status codes (e.g., 200, 403, 404, 504)

Database Topics

Types of MySQL locks and how deadlocks occur

Reasons and methods for sharding and partitioning

Differences among CHAR, VARCHAR, and TEXT

JOIN types, especially LEFT JOIN and handling of NULLs

B‑Tree vs hash index differences

Techniques for query optimization

Overview of NoSQL databases and their contrast with relational databases

Common Redis storage types

Linux Section

Frequently used Linux and Git commands and their purposes

Commands to view current processes and other useful system operations

Django Project Section

Briefly describe the project you worked on, regardless of backend relevance

Identify the most challenging part and how you solved it

Experience reading Django admin source code or Flask source code; thoughts on open source

Explain MVC/MTV architecture

How caching is used

Purpose of middleware

What CSRF is and how Django mitigates it; also XSS considerations

Design a simple login flow

Difference and relationship between session and cookie; why sessions are considered secure

Roles of uWSGI and Nginx

If you can answer these questions, you are ready to try a junior web backend interview. Good luck!