App Engine - Output Response Time
Call start = time.time() as the very first operation in your handling scripts, and, when you're just about done with everything, as the very last thing you output use (a properly formatted version of) time.time() - start.
If you're using templates for your output (e.g., the Django templates that come with app engine -- 0.96 by default, though you can explicitly ask for newer and better ones;-), or jinja2, mako, ...), it's important to be able to use in those templates a tag or filter to request and format such an expression. (You don't want to compute it at the time you call the template's render method, and pass it as part of that method's context, or else you'll fail to account for all the template rendering time in your estimate of "response time"!-).  You may have to code and inject such a tag or filter into the "templating language" if your chosen templating language and version doesn't already supply one but is at least minimally extensible;-).
`
Say I wanted to print the response time on my pages like Google do. 
How would I go about doing this?