Logging with CherryPy doesn't work

Question

I use cherrypy.

I have the following definition:

import cherrypy
cherrypy.config.update({'log.error_file': '/var/log/Web.log',
                'log.access_file': '/var/log/Access.log'
               })
from cherrypy import wsgiserver

if __name__ == '__main__':
   d = wsgiserver.WSGIPathInfoDispatcher({'/': app})
   server = wsgiserver.CherryPyWSGIServer(('0.0.0.0', 5877), d)
   try:
       server.start()
   except KeyboardInterrupt:
       server.stop()

When I see the logs, It doesn't contain anything.

What can be the reason? Am I missed some definition?