Python corountine examples

coroutines.py

def recv_count():
    try:
        while True:
             n = (yield)
             print "T-minus", n
    except GeneratorExit:
        print "Kaboom!"

def ex1():
    r = recv_count()
    r.next() # initialize iterator

    for i in range(5,0,-1):
        r.send(i)

    r.close()

#####

def counter(x):
    n = 0
    while n <= x:
        v = (yield n)
        if v is not None:
            n = v
        else:
            n += 1

def ex2():
    gen = counter(25)
    for i in gen:
        print i
        if i == 15: # jump directly to 18
            gen.send(18)
#####

def gen():
    for i in range(0, 10):
        # yields i and receives v from send
        v = (yield i)
        print "from send", v
        # need to yield because send is waiting for an answer
        yield "hello"

def ex3():
    g = gen()
    for i in g:
        print "from 1st yield", i
        v = g.send(i**2)
        print "from 2nd yield", v

def ex4():
    g = gen()
    i = g.next()
    print i
    v = g.send(i**2)
    print v

#####

class StopPower(Exception):
    pass

def powertable():
    for i in (2,3):
        j = 1
        while True:
            try:
                yield j, j ** i
                j += 1
            except StopPower:
                yield
                print "stopped"
                break

def ex5():
    it = powertable()
    for j, jpower in it:
        print j, jpower
        if jpower > 100:
            it.throw(StopPower)

if __name__ == "__main__":
    import sys
    import __main__
    getattr(__main__, "ex" + str(sys.argv[1]))()