4.2 Overview of a Handler

A handler is a function that processes a particular phase of a request. Apache processes requests in phases - read the request, process headers, provide content, etc. For every phase, it will call handlers, provided by either the Apache core or one of its modules, such as mod_python, which passes control to functions provided b the user and written in Python. A handler written in Python is not any different than a handler written in C, and follows these rules:

 A handler function will always be passed a reference to a Request object. (Throughout this manual, the Request object is often referred to by the req variable.)

Every handler can return:

As an alternative to returning an HTTP error code, handlers can signal an error by raising the apache.SERVER_RETURN exception, and providing an HTTP error code as the exception value, e.g.


Handlers can send content to the client using the Request.write() method. Before sending the body of the response, headers must be sent using the Request.send_http_header() method.

Client data, such as POST requests, can be read by using the Request.read() function.

NOTE: The directory of the Apache Python*Handler directive in effect is prepended to the sys.path. If the directive was specified in a server config file outside any <Directory>, then the directory is unknown and not prepended.

An example of a minimalistic handler might be:

from mod_python import apache

def requesthandler(req):
    req.content_type = "text/plain"
    req.write("Hello World!")
    return apache.OK