defer-cancel-6.py

from twisted.internet import defer

def canceller(d):
    print("I need to cancel this deferred:", d)
    print("Firing the deferred with a result")
    d.callback('result')

def callback(res):
    print('callback got:', res)

def errback(err):
    print('errback got:', err)

d = defer.Deferred(canceller) # created by lower-level code
d.addCallbacks(callback, errback) # added by higher-level code
d.cancel()
print('done')