Does anyone have a preferred method for handling AWS credentials for work in boto3? Especially when working with code stored in GitHub via Working Copy?

Basically, I work on the code from a regular Mac and from my iPad, so I don't want the credentials hard coded or loaded in a file on GitHub.

I tried creating a ~./aws/credentials file but that didn't seem to work. Is there a way to set environment variables that last between sessions? (or that I can set quickly with a script). Or a file location that someone has found to work?

Thanks