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"""Example of doing arbitarily long calculations nicely in Twisted.
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This is also a simple demonstration of twisted.protocols.basic.LineReceiver.
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This example uses generators to do the calculation. It also tries to be
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a good example in division of responsibilities:
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- The protocol handles the wire layer, reading in lists of numbers
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and writing out the result.
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- The factory decides on policy, and has relatively little knowledge
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of the details of the protocol. Other protocols can use the same
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factory class by intantiating and setting .protocol
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- The factory does little job itself: it is mostly a policy maker.
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The 'smarts' are in free-standing functions which are written
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The goal is for minimal dependencies:
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- You can use runIterator to run any iterator inside the Twisted
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- You can use multiply whenever you need some way of multiplying
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numbers such that the multiplications will happen asynchronously,
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but it is your responsibility to schedule the multiplications.
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- You can use the protocol with other factories to implement other
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functions that apply to arbitrary lists of longs.
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- You can use the factory with other protocols for support of legacy
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protocols. In fact, the factory does not even have to be used as
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a protocol factory. Here are easy ways to support the operation
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class Multiply(xmlrpc.XMLRPC):
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def __init__(self): self.factory = Multiplication()
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def xmlrpc_multiply(self, *numbers):
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return self.factory.calc(map(long, numbers))
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class Multiply(pb.Referencable):
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def __init__(self): self.factory = Multiplication()
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def remote_multiply(self, *numbers):
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return self.factory.calc(map(long, numbers))
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Multiplying zero numbers is a perfectly sensible operation, and the
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result is 1. In that, this example departs from doc/examples/longex.py,
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which errors out when trying to do this.
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from __future__ import generators
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from twisted.protocols import basic
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from twisted.internet import defer, protocol
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def runIterator(reactor, iterator):
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reactor.callLater(0, runIterator, reactor, iterator)
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def multiply(numbers):
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class Numbers(basic.LineReceiver):
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"""Protocol for reading lists of numbers and manipulating them.
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It receives a list of numbers (seperated by whitespace) on a line, and
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writes back the answer. The exact algorithm to use depends on the
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factory. It should return an str-able Deferred.
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def lineReceived(self, line):
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numbers = map(long, line.split())
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self.sendLine('Error.')
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deferred = self.factory.calc(numbers)
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deferred.addCallback(str)
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deferred.addCallback(self.sendLine)
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class Multiplication(protocol.ServerFactory):
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"""Factory for multiplying numbers.
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It provides a function which calculates the multiplication
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of a list of numbers. The function destroys its input.
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Note that instances of this factory can use other formats
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for transmitting the number lists, as long as they set
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correct protoocl values.
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def calc(self, numbers):
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deferred, iterator = multiply(numbers)
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from twisted.internet import reactor
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runIterator(reactor, iterator)
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if __name__ == '__main__':
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from twisted.internet import reactor
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reactor.listenTCP(1234, Multiplication())