Years ago, one of my friends in college was taking an intro to CS class. He asked me for help on one of his assignments. It was a simple Python program, but it wasn't running as expected. I go in figuring it will be easy to fix. But everything looks exactly right. An hour later I'm tearing my hair out! It isn't even entering the function although it's clearly called. I'm beginning to feel very self conscious, as a CS major who can't even debug a 15 line program for a friend.

Then it hit me. This is Python. I used an editor macro to convert all indentation to tabs, lined them up, and it ran on the first try. Turns out, he had somehow ended up with a mixture of tabs and spaces.

I'm not sure what the takeaway is, but I think he got a surprisingly honest introduction to the life of a developer...