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"""Simple example of doing arbitrarily long calculations nicely in Twisted.
This is also a simple demonstration of twisted.protocols.basic.LineReceiver.
"""
from twisted.internet import reactor
from twisted.internet.protocol import ServerFactory
from twisted.protocols import basic
class LongMultiplicationProtocol(basic.LineReceiver):
"""A protocol for doing long multiplications.
It receives a list of numbers (separated by whitespace) on a line, and
writes back the answer. The answer is calculated in chunks, so no one
calculation should block for long enough to matter.
"""
def connectionMade(self):
self.workQueue = []
def lineReceived(self, line):
try:
numbers = [int(num) for num in line.split()]
except ValueError:
self.sendLine(b"Error.")
return
if len(numbers) <= 1:
self.sendLine(b"Error.")
return
self.workQueue.append(numbers)
reactor.callLater(0, self.calcChunk)
def calcChunk(self):
# Make sure there's some work left; when multiple lines are received
# while processing is going on, multiple calls to reactor.callLater()
# can happen between calls to calcChunk().
if self.workQueue:
# Get the first bit of work off the queue
work = self.workQueue[0]
# Do a chunk of work: [a, b, c, ...] -> [a*b, c, ...]
work[:2] = [work[0] * work[1]]
# If this piece of work now has only one element, send it.
if len(work) == 1:
self.sendLine(str(work[0]).encode("ascii"))
del self.workQueue[0]
# Schedule this function to do more work, if there's still work
# to be done.
if self.workQueue:
reactor.callLater(0, self.calcChunk)
class LongMultiplicationFactory(ServerFactory):
protocol = LongMultiplicationProtocol
if __name__ == "__main__":
import sys
from twisted.python import log
log.startLogging(sys.stdout)
reactor.listenTCP(1234, LongMultiplicationFactory())
reactor.run()
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