Generating a Page Dynamically¶

The goal of this example is to show you how to dynamically generate the contents of a page.

Taking care of some of the necessary imports first, we’ll import Site, the reactor, and endpoints :

from twisted.internet import reactor, endpoints
from twisted.web.server import Site

The Site is a factory which associates a listening port with the HTTP protocol implementation. The reactor is the main loop that drives any Twisted application. Endpoints are used to create listening ports.

Next, we’ll import one more thing from Twisted Web: Resource . An instance of Resource (or a subclass) represents a page (technically, the entity addressed by a URI).

from twisted.web.resource import Resource

Since we’re going to make the demo resource a clock, we’ll also import the time module:

import time

With imports taken care of, the next step is to define a Resource subclass which has the dynamic rendering behavior we want. Here’s a resource which generates a page giving the time:

class ClockPage(Resource):
    isLeaf = True
    def render_GET(self, request):
        return (b"<!DOCTYPE html><html><head><meta charset='utf-8'>"
                b"<title></title></head><body>" + time.ctime().encode('utf-8'))

Setting isLeaf to True indicates that ClockPage resources will never have any children.

The render_GET method here will be called whenever the URI we hook this resource up to is requested with the GET method. The byte string it returns is what will be sent to the browser. In this case, that byte string is an HTML 5 web page encoded as UTF-8.

With the resource defined, we can create a Site from it:

resource = ClockPage()
factory = Site(resource)

Just as with the previous static content example, this configuration puts our resource at the very top of the URI hierarchy, ie at / . With that Site instance, we can tell the reactor to create a TCP server and start servicing requests:

endpoint = endpoints.TCP4ServerEndpoint(reactor, 8880)
endpoint.listen(factory)
reactor.run()

Here’s the code with no interruptions:

from twisted.internet import reactor, endpoints
from twisted.web.server import Site
from twisted.web.resource import Resource
import time

class ClockPage(Resource):
    isLeaf = True
    def render_GET(self, request):
        return (b"<!DOCTYPE html><html><head><meta charset='utf-8'>"
                b"<title></title></head><body>" + time.ctime().encode('utf-8'))

resource = ClockPage()
factory = Site(resource)
endpoint = endpoints.TCP4ServerEndpoint(reactor, 8880)
endpoint.listen(factory)
reactor.run()