Wednesday, May 21, 2014

Python 'or'

I've been trying to write more Pythonic code. I'm sure everyone has their own definition of what Pythonic is, but everyone will agree on things like using list/dict comprehensions where possible and so on and so forth.

I was perusing some code written by some colleagues and found this:

    push_data = {'message': container.message or 'NO COMMIT MESSAGE',

This took me to the basic definition of Python's or keyword and, notably, this clause: "These only evaluate their second argument if needed for their outcome."

Way cool! I would previously have used a construction like

    push_data = {'message': container.message if container.message else 'NO COMMIT MESSAGE',

and patted myself on the back for being Pythonic, but there is an even better way to do it.

I must say, though, that I would not use the corresponding and construction because it is not so intuitive to me.

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