When a tutorial suggests installing a Python package via pip or easy_install, how might one determine where the original official code repository is?
For instance, the Python Yelp API Examples suggest installing sudo easy_install oauth2 however I would prefer to download the packages myself from the official repo. I've googled for python oauth and found quite a few 'competing' packages. I think that this one is the official package (due to being linked from here) but I would like to know which chain of examination would lead to the official package source code?
There is no one way to determine the repo of a package listed on PyPI. It is up to the author to document this for you.
When you use easy_install oauth2, you instruct easy_install to load the PyPI-registered project oauth2, located at https://pypi.python.org/pypi/<project-name>, which should be your first port of call if you are looking for repository information.
The oauth2 PyPI page documents a homepage: https://github.com/simplegeo/python-oauth2
This is the link provided in the setup.py metadata for this project, and that's as far as you get with examining this. If the author put in the wrong link, then there is little you can do to verify this.
To me, there is no doubt that https://github.com/simplegeo/python-oauth2/ is the source code you'd install when you run easy_install oauth2.