At PyCon UK 2014 I gave a talk about The Twelve-Factor App, “a methodology for building software-as-a-service apps”. The Twelve-Factor stance on config – “store [it] in the environment” – is probably the most misunderstood.
I want those misunderstandings to stop. If you feel you disagree with 12factor, or you feel you don’t quite see the benefit or how to do it, then please keep reading. If you’re still not sure afterwards, drop me an email, or find me on IRC; I’d love to talk more.
If you take just one thing away from here, please make it this: 12factor says your applications should read their config from the environment; it has very little to say about how you populate the environment – use whatever works for you