Now that we know about the two modes of request handling in Google App Engine, how they work, and their respective pros and cons, it's time to divert our attention to request handlingfrom another aspect. As we discussed in the previous chapter, app.yaml is a manifest of your application, and it defines what your application really is. One of the major things that it defines is how your application processes URLs. There are three things that app.yaml defines:
Which URLs or URL patterns are processed?
In what order are the URLs or URL patterns processed?
How exactly are the URLs or URL patterns processed?
To define which URLs are processed, you can define absolute URLs that start with the / character. Alternatively, if you want some flexibility, you can use regular expressions. Regular expressions might contain regular expression groups, which can later be used in a handler description to specify the URL patterns. We will see this in an example shortly.
The next thing...