[Edu-sig] old macdonald had a farm (coroutines for noobs like me)

[kirby urner]

"""
On the Farm: (Python 3 -- 3to2 easy)

for David Beazley, the gratitude, who wanted
something more useful than Fibonacci numbers

See:
http://oubiwann.blogspot.com/2009/04/generators-and-coroutines.html
(my comments appended)
"""

def coroutine(target):
    """
    used to decorate generators we plan to
    use as coroutines
    """
    def initialize(*args, **kwargs):
        thegen = target(*args, **kwargs)
        next(thegen)
        return thegen
    return initialize

@coroutine
def screening(target, farmanimals):
    var = ""
    while True:
        var = (yield)
        print("I am a %s" % var)
        if var in farmanimals:
            target.send(var)

@coroutine
def process():
    while True:
        var = (yield)
        print("Farm animal %s is being processed." % var)

def test():
    """
    >>>
    I am a cow
    Farm animal cow is being processed.
    I am a jackalope
    I am a pig
    Farm animal pig is being processed.
    I am a monkey
    """
    onthefarm = ["cow","pig","chicken"]
    p2 = process()
    p1 = screening(p2, onthefarm)
    p1.send("cow")
    p1.send("jackalope")
    p1.send("pig")
    p1.send("monkey")

if __name__ == "__main__":
    test()