There is CGIHandler that ships with python. Not many examples that are simple, so...

  #!/usr/bin/env python
  from wsgiref.handlers import CGIHandler

  def app(environ, start_response):
    start_response('200 OK', [('Content-Type', 'text/html')])
    return [
      b"<html><head><title>foo</title></head><body>bar</body></html>"
    ]

  if __name__ == '__main__':
    CGIHandler().run(app)