PyCon NL 2025 - Race to the Root Cause by Klaas van Schelven

How fast can you really debug a Python stacktrace? This talk is a rapid-fire challenge where we throw real-world-inspired stacktrace puzzles at the audience. Can you spot what actually happened before the reveal? Each puzzle starts with a snippet of code and a misleading or confusing stacktrace, and the audience gets to play along as we unravel what’s really going on under the hood. Examples include: * Chained Exception Puzzle: Python’s “During handling of the above exception, another exception occurred” messages rarely make the real flow obvious. We’ll see how these stacktraces force you to piece together what actually happened. * The Missing Curly Bracket: Sometimes Python blames a line with a with statement, even though no code runs there. Why does this happen? And what does it have to do with curly brackets? By the end, you’ll have a better feel for Python’s stacktraces, some new strategies for debugging faster, and at least one story to share the next time a stacktrace tries to trick you. You’ll walk away with sharper debugging instincts, some practical tricks, and maybe a laugh at Python’s expense. If you’ve ever felt outsmarted by a stacktrace, this is your chance to race to the root cause — and win.