The way to go is wsgi.
WSGI is the Web Server Gateway Interface. It is a specification for web servers and application servers to communicate with web applications (though it can also be used for more than that). It is a Python standard, described in detail in PEP 333.
All current frameworks support wsgi. A lot of webservers support it also (apache included, through mod_wsgi). It is the way to go if you want to write your own framework.
Here is hello world, written to wsgi directly:
def application(environ, start_response):
status="200 OK"
response_headers = [('Content-type','text/plain')]
start_response(status, response_headers)
return ['Hello world!\n']
Put this in a file.py, point your mod_wsgi apache configuration to it, and it will run. Pure python. No imports. Just a python function.
If you are really writing your own framework, you could check werkzeug. It is not a framework, but a simple collection of various utilities for WSGI applications and has become one of the most advanced WSGI utility modules. It includes a powerful debugger, full featured request and response objects, HTTP utilities to handle entity tags, cache control headers, HTTP dates, cookie handling, file uploads, a powerful URL routing system and a bunch of community contributed addon modules. Takes the boring part out of your hands.