Ouvert

(ouvert means open in French)

Last week I contributed a small feature to clize. As before, I discovered this project on the GitHub page for trending Python repositories. The author had a list of open issues for the repository which made it easy to see what needed to be worked on and I picked one that caught my fancy.

Once I knew what needed to be done I had to figure out how to implement it. The first thing I did was see how the existing code handled unknown command line arguments. “Oh look, it printed ‘Unknown option’! That seems like a good place to start.” I ran an ack for the phrase “Unknown option” and found the relevant source code files. The next step was to figure out from where the parsed arguments lived inside the program. A well placed print statement that I added quickly solved that mystery.

With this knowledge in hand I began writing some code. The basic algorithm was pretty simple – in case the user enters a command line argument that is not one of the parsed arguments compute the Levenshtein distance between what the user entered and the known arguments and suggest one that has the lowest distance. This was more or less the initial pull request that I submitted. The author provided excellent feedback on my code and after a couple of iterations my commit was merged into the master branch.

Things I learnt along the way –

• The existence of difflib. I had no idea this fantastic module was a part of the Python Standard Library.
• Functional programming in Python is awesome.