Making use of twisted coiterate...

coiterate_01.py

# -*- coding: utf-8 -*-
"""
Making use of twisted coiterate
example 01
"""

from twisted.internet import reactor
from twisted.internet.task import coiterate

def make_iterator_to_sum_all_integers_until(N):

    s = 0
    for i in xrange(N):
        s += i
        print "Adding %i to result" % i
        yield None # event loop can looks after other things...

    print "result is %i " % s

def sum_all_integers_being_nice_to_reactor(N):

    all_sum_steps = make_iterator_to_sum_all_integers_until(N)
    coiterate(all_sum_steps)

reactor.callLater(0, sum_all_integers_being_nice_to_reactor, 8)
reactor.run()

coiterate_02.py

# -*- coding: utf-8 -*-
"""
Making use of twisted coiterate
example 02 : Obtaining coiteration result...
"""

from twisted.internet import reactor
from twisted.internet.task import coiterate

def make_iterator_to_sum_all_integers_until(N, context):

    s = 0
    for i in xrange(N):
        s += i
        print "Adding %i to result" % i
        yield None # event loop can looks after other things...

    context['result'] = s

def sum_all_integers_being_nice_to_reactor(N):
    "return Deferred firing calculated sum..."

    def extract_result_cb(ignored, context):
        "return context['result']"

        rv = context['result']
        print "Got result = %s" % rv
        return rv

    context = {}
    all_sum_steps = make_iterator_to_sum_all_integers_until(N, context)

    deferred = coiterate(all_sum_steps)
    deferred.addCallback(extract_result_cb, context)

    return deferred

reactor.callLater(0, sum_all_integers_being_nice_to_reactor, 8)
reactor.run()

coiterate_03.py

# -*- coding: utf-8 -*-
"""
Making use of twisted coiterate
example 03 : Waiting for Deferred...
"""
from twisted.internet import reactor
from twisted.internet.task import coiterate, deferLater

def make_iterator_to_sum_all_integers_until(N, context):

    def wait_some_time(t):
        "return Deferred firing after t seconds"

        return deferLater(reactor,t,lambda :"I was paused %.02f seconds"%t)

    def print_pause_cb(msg):
        "callback printing result message..."

        print msg

    s = 0
    for i in xrange(N):
        
        s += i
        print "Adding %i to result" % i

        d = wait_some_time(1.0)
        d.addCallback(print_pause_cb)
        yield d    # we will be paused until d fires...

    context['result'] = s


def sum_all_integers_being_nice_to_reactor(N):
    "return Deferred firing calculated sum..."

    def extract_result_cb(ignored, context):
        "return context['result']"

        rv = context['result']
        print "Got result = %s" % rv
        return rv

    context = {}
    all_sum_steps = make_iterator_to_sum_all_integers_until(N, context)

    deferred = coiterate(all_sum_steps)
    deferred.addCallback(extract_result_cb, context)

    return deferred

reactor.callLater(0, sum_all_integers_being_nice_to_reactor, 8)
reactor.run()

coiterate_04.py

# -*- coding: utf-8 -*-
"""
Making use of twisted coiterate
example 04 : Cancelling coiteration...
"""

from twisted.internet import reactor
from twisted.internet.defer import Deferred, CancelledError
from twisted.internet.task import coiterate, deferLater

def make_iterator_to_sum_all_integers_until(N, context):

    def wait_some_time(t):
        "return Deferred firing after t seconds"

        return deferLater(reactor,t,lambda :"I was paused %.02f seconds"%t)

    def print_pause_cb(msg):
        "callback printing result message..."

        print msg

    d = None
    s = 0

    try:

        for i in xrange(N):
            
            s += i
            print "Adding %i to result" % i

            d = wait_some_time(1.0)
            d.addCallback(print_pause_cb)
            yield d    # we will be paused until d fires...

        context['result'] = s

    except GeneratorExit:

        print "---"
        print "Early termination..."

        # cancel pending Defferred
        if d and not d.called:
            d.cancel()

def sum_all_integers_being_nice_to_reactor(N):
    "return Deferred firing calculated sum..."

    def extract_result_cb(ignored, context):
        "return context['result']"

        rv = context['result']
        return rv

    def suppress_cancel_log_eb(error):
        "trap CancelledError"

        # this suppress UnhandledError warning...
        error.trap(CancelledError)

    context = {}
    all_sum_steps = make_iterator_to_sum_all_integers_until(N, context)

    deferred = Deferred(lambda _:all_sum_steps.close())
    coiterate(all_sum_steps).chainDeferred(deferred)
    deferred.addCallback(extract_result_cb, context)
    deferred.addErrback(suppress_cancel_log_eb)
    return deferred

def main():
    "start summing integers and stop after 3 seconds..."
    
    def print_result_cb(res):
        "print result if any..."
        
        if res is not None:
            print "Got result = %s" % res

    # start sum calculation using coiteration...
    d = sum_all_integers_being_nice_to_reactor(8)
    d.addCallback(print_result_cb)

    # schedule cancellation after 3.00 seconds
    reactor.callLater(3.0, d.cancel)


reactor.callLater(0, main)
reactor.run()