We’ll take a look at some Python code that has a strange integer bug in it. You’ll learn about how the bug was discovered, and by the end of the talk you’ll understand why it’s a bug and why the bug only occurs with larger integers. You’ll see a one character fix to the bug, and then an even better fix. We’ll look at CPython's longobject.c source code to understand how smaller integers are handled differently than larger ones. We’ll explore the difference between comparing values in Python versus testing for identity. Hopefully you’ll gain an appreciation that bugs can be your best teachers and be able to prevent more bugs.