Comment by ljm

I love programmer stories like this. My favourite personal experience was on my first Ruby on Rails project after first moving to London. I was pretty green at the time, having had only a few years of PHP experience under my belt and little else.

We had to build a Rails app around a poker game. We didn't own the source to the poker game or its API, but we had to embed it nonetheless. We had this really strange issue where some people, under a certain circumstance, couldn't get into the game. It would just boot them out. Me and my team mate must have poured through the Ruby code dozens and dozens of times and found no evidence of this bug, no ability to reproduce it; bearing in mind I was still learning the ropes and jumping head first into an unfamiliar codebase is quite daunting.

Eventually I decide to get my hands dirty and I start poking into this game engine. We embedded it as s flash widget, but the server doing most of the work was written in a mix of C++ and Python. I didn't fully comprehend what I was looking at but, even though things looked suspicious, I couldn't put my finger on an actual problem until I looked at the API written in Flask and noticed that one line of code didn't look like any other.

    some_value = params['some_key']

If the request didn't contain the parameter `some_key` then this would raise a KeyError.

After maybe three solid weeks of trying to debug this thing, I submitted a one line patch:

    some_value = params.get('some_key')

It's not quite as weird or as fun as most examples but for me personally it was such a great lesson in debugging and being curious about unfamiliar stuff, rather than closed off or afraid.