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- #!/usr/bin/env python
- # https://twistedmatrix.com/documents/16.2.0/core/howto/defer.html
- 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
- print("return result (x*3) in 2 sec...")
- reactor.callLater(2, deferred.callback, inputData * 3)
- return deferred
- def cbPrint(result):
- print("cbPrint({0})".format(result))
- # doing eferred, or the return result + 1 works
- print("return result (x+1) in 1 sec...")
- deferred = defer.Deferred()
- reactor.callLater(1, deferred.callback, result + 1)
- return deferred
- # return result + 1
- def cbPrint2(result):
- print("cbPrint2({0})".format(result))
- print("return result (x+2) ...")
- # print("(this isn't a defer)") # it is now! :P
- # return a Deferred object already called back with the value of result
- return defer.succeed(result + 2)
- # 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)
- d.addCallback(print)
- print("Stop the reactor in 7 seconds...")
- reactor.callLater(7, reactor.stop)
- print("starting the reactor")
- reactor.run()
- print("Reactor has been safely shutdown. :P")
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