[Twisted-Python] Getting the hang of twisted.web

Micah Yoder micahlists at comcast.net
Sun Aug 3 02:38:06 EDT 2003

Ok, I have the following in web.py:

from twisted.web import resource

class Simple(resource.Resource):
    isLeaf = True
    def render(self, request):
        return "<html>Hello, world!</html>"

class Hello(resource.Resource):

    def __init__(self):
      self.putChild('simple', Simple())

    def getChild(self, name, request):
        if name == '':
            return self
        return Resource.getChild(
            self, name, request)

    def render(self, request):
      s = request.getSession()
      if not hasattr(s, 'var'):
        s.var = 1
        s.var = s.var * 2
      return """<html>
      Hello, world! I am located at %r and am at %d. My args are %s. Site %s.
    </html>"""               % (request.prepath, s.var, repr(request.args), 


Then I:

$ mktap web --class=web.Hello
$ twistd -f web.tap

Seems to work fine.  I can go to http://localhost:8080/ to get the Hello() 
class and http://localhost:8080/simple to get the Simple() class.


1. Is there anything I'm doing obviously wrong or a "non-Twisted" way, like 
with the session variable or the child stuff?

2. What about persistant HTTP sessions?  I thought one of the points of this 
mktap stuff was to allow persistance in protocols.  I do:
$ killall twistd
$ twistd -f web-shutdown.tap
and go to the index page again and the counter gets re-started at 1.  Can't 
they be made to persist?

3. Finally, some advice on how to structure my "real" project would be 
appreciated.  I have a program that will store and index a large amount of 
data (several megabytes), and intend to have resources that search and 
display it.  The original importing of the data takes several seconds now, 
and will take probably a minute or more by the time I'm done.  The data is 
being stored in a Python class, with methods to set it up and search it, 
along with direct public instance-variable access to some structures.

The question is, where should this class object be stored in a .tap-ified 
program?  Right now I have the class instance as a global variable in the 
module that my related resource objects are in, but that doesn't seem ideal.  
I thought about storing it in the Site() object, but there doesn't seem to be 
a way to access the Site object from a resource request.  request.site only 
returns None ... is ths a bug?

(Yes, I've been doing this application so far with just a reactor and a Site() 
object.  But it seems prudent to try to .tap-ify it.)


Yoder Internet Development
Honest and Affordable Web Development and Linux consulting

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