Python's += Operator Is Lying to You (And Here's the Proof)

📰 Dev.to · Ameer Abdullah

Discover the unexpected behavior of Python's += operator and how it can lead to bugs in your code

intermediate Published 27 Jun 2026

Action Steps

Run a Python script with a list and use the += operator to append elements
Compare the results of using += with other methods like extend() or append()
Test the behavior of += with different data types, such as strings or integers
Use the id() function to verify the memory location of variables before and after using +=
Apply this knowledge to debug and optimize your own Python code

Who Needs to Know This

All developers, especially those working with Python, can benefit from understanding the nuances of the += operator to write more robust code

Key Insight

💡 The += operator in Python does not always behave as expected, especially when working with mutable objects like lists

Key Takeaways

Discover the unexpected behavior of Python's += operator and how it can lead to bugs in your code

I want to show you something that has confused developers at every skill level, from beginners to...