doc/web/howto/listings/wait_for_it.py

   1 import sys
   2 from twisted.web.template import XMLString, Element, renderer, flatten
   3 from twisted.internet.defer import Deferred
   4
   5 sample = XMLString(
   6     """
   7     <div xmlns:t="http://twistedmatrix.com/ns/twisted.web.template/0.1">
   8     Before waiting ...
   9     <span t:render="wait"></span>
  10     ... after waiting.
  11     </div>
  12     """)
  13
  14 class WaitForIt(Element):
  15     def __init__(self):
  16         Element.__init__(self, loader=sample)
  17         self.deferred = Deferred()
  18
  19     @renderer
  20     def wait(self, request, tag):
  21         return self.deferred.addCallback(
  22             lambda aValue: tag("A value: " + repr(aValue)))
  23
  24 def done(ignore):
  25     print("[[[Deferred fired.]]]")
  26
  27 print('[[[Rendering the template.]]]')
  28 it = WaitForIt()
  29 flatten(None, it, sys.stdout.write).addCallback(done)
  30 print('[[[In progress... now firing the Deferred.]]]')
  31 it.deferred.callback("<value>")
  32 print('[[[All done.]]]')