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Python Code Review Guide

The most common Python bugs, security vulnerabilities, and code quality issues — with real code examples and step-by-step fixes. Covers Django, Flask, FastAPI, and standard Python.

What makes Python code review different?

Python's dynamic typing makes certain bugs extremely common — and easy to miss. Unlike compiled languages, Python won't catch most bugs until the specific code path executes. The mutable default argument trap, NoneType errors, and SQL injection via f-strings are unique to Python's runtime model.

Security Vulnerabilities

5 guides

Python security issues ranked by real-world exploit frequency (OWASP Top 10, 2024).

Security

SQL Injection in Python

Security

XSS in Python Flask

Security

Command Injection

Security

Path Traversal

Security

Hardcoded Secrets

Common Bugs

5 guides
Bug

NoneType Error

Bug

Index Out of Range

Bug

Async/Await Mistakes

Bug

Mutable Default Argument

Bug

Infinite Loop

Code Quality

5 guides
Code Quality

Dead Code

Code Quality

Unused Imports

Code Quality

Long Functions

Code Quality

Global Variable Abuse

Tool

Python Bug Detector

Python review checklist — 5 things to always check

  1. No mutable default arguments
  2. All database queries use parameterized queries
  3. No hardcoded secrets — use environment variables
  4. subprocess calls never use shell=True with user input
  5. All user-controlled file paths validated with os.path.realpath()

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Published by LearnCodeGuide Team · Last reviewed: October 2025