google.com web pages with ".py" extension?
Yes, this just accesses a resource called answer.py on the server. This naming convention is entirely up to the server - it could run a python script (most likely what is going on), or it could even be in a completely different language. In any case, all that that browser cares about is the information that is returned from that resource - HTML, CSS, XML, etc...
Take, for instance, support.google.com/mail/bin/answer.py?hl=en&answer=13287. What is that answer.py? How does this work? I'm 99.99% sure that browsers don't have the ability to interpret python code (yet) like javascript / PHP. So what is this? Is it some Python webframework?