wsgitimer.py

import functools

class TimerMiddleware(object):
    'a WSGI middleware that sends an X-Response-Time header'
    def __init__(self, app):
        self.app = app

    def start_response(self, default, start_time, status, headers):
        headers = headers[:] + [('X-Response-Time', time.time() - start_time)]
        return default(status, headers)
        
    def __call__(self, environ, start_response):
        return self.app(environ, functools.partial(
            self.start_response, start_response, time.time()))