Practical server side includes with Python on Google App Engine
Or use a framework like django, which will help in inheritance of templates.
Is there a decent way to "simulate" server side includes using Python on Google App Engine?
I would really like to split my static html files up into smaller pieces for two reasons:

They will be easier to manage from a development perspective
HTML that is redundant across multiple pages can be more easily re-used and updates to the HTML will show on all pages instead of having to copy and paste updates