twgs-proxy/defer.py

#!/usr/bin/env python

from twisted.internet import reactor, defer
from pprint import pprint

def getData(inputData):
    print('getData({0})'.format(inputData))
    deferred = defer.Deferred()
    # simulate a delayed result by asking reactor
    # to fire in 2 seconds with inputData * 3 as result
    reactor.callLater(2, deferred.callback, inputData * 3)
    return deferred

def cbPrint(result):
    print("result: {0}".format(result))
    # doing eferred, or the return result + 1 works
    deferred = defer.Deferred()
    reactor.callLater(1, deferred.callback, result + 1)
    return deferred
    # return result + 1

def cbPrint2(result):
    print("result:")
    pprint(result)
    return result + 2

d = getData(3)
# Ok, chaining callbacks is ... different.

d.addCallback(cbPrint)
# Before return result, this was printing None.  
d.addCallback(cbPrint2)
d.addCallback(cbPrint)

reactor.callLater(5, reactor.stop)
print("starting the reactor")
reactor.run()