twisted_defer.py

# based from twisted doc
# https://twistedmatrix.com/documents/16.5.0/core/howto/defer.html

from twisted.internet import reactor, defer

def getDeferredObj(inputData):
    print('getDeferredObj called')
    deferred = defer.Deferred()
    # simulate a delayed result by asking the reactor to fire the
    # Deferred in 2 seconds time with the result inputData * 3
    reactor.callLater(2, deferred.callback, inputData * 3)
    return deferred

def printDataCallback(result):
    """
    this function is called asynchronous by twisted
    """
    print('Result received: {}'.format(result))
    # stopping reactor manually
    reactor.stop()

deferred = getDeferredObj(3)
deferred.addCallback(printDataCallback)


# start up the Twisted reactor (event loop handler) manually
print('Starting the reactor')
reactor.run()

# RESULT
# getDeferredObj called
# Starting the reactor
# Result received: 9