Using the Users API is a very simple and flexible way to work the authentication in App Engine, but please make sure that your application cases don't require more elements for the authentication environment.
Note: If you need more information about the traditional structure of an App Engine app, please review this info.
The Users API allows:
Important elements into the view:
from google.appengine.api import users
User-object and methods:
user = users.get_current_user()
Note: the implementation of jinja2 is optional, but into the article is used to explaining the completely workflow.