# Why Your Python Functions Are Secretly Changing Data You Never Passed to Them

Page: https://stenobird.com/podcast/programming-tech-brief-by-hackernoon-6364125/why-your-python-functions-are-secretly-changing-data-you-never-passed-to-them
Text version: https://stenobird.com/podcast/programming-tech-brief-by-hackernoon-6364125/why-your-python-functions-are-secretly-changing-data-you-never-passed-to-them.md
Podcast: [Programming Tech Brief By HackerNoon](https://stenobird.com/podcast/programming-tech-brief-by-hackernoon-6364125)
Published: 2026-05-28T16:00:47+00:00
Episode link: https://share.transistor.fm/s/8200f3d9
Audio file: https://media.transistor.fm/8200f3d9/cfebd11d.mp3
Processing state: not_requested
JSON: https://stenobird.com/v1/public/podcasts/programming-tech-brief-by-hackernoon-6364125/episodes/why-your-python-functions-are-secretly-changing-data-you-never-passed-to-them
Duration seconds: 498

## Resource

This story was originally published on HackerNoon at: https://hackernoon.com/why-your-python-functions-are-secretly-changing-data-you-never-passed-to-them . Python's mutable default bug silently grows your lists across calls. Learn why it happens, how to fix it, and when it's actually intentional. Check more stories related to programming at: https://hackernoon.com/c/programming . You can also check exclusive content about #python , #python-programming , #python-tutorials , #python-debugging , #mutable-objects , #python-functions , #bugs , #hackernoon-top-story , and more. This story was written by: @sohelalam79 . Learn more about this writer by checking @sohelalam79's about page, and for more stories, please visit hackernoon.com . You defined a function with a list as a default argument. Now, it's accumulating data across calls you never connected.

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