send() to a generator in a "for" loop with continue(val)??

[Dale Roberts]

I've started using generators for some "real" work (love them!), and I
need to use send() to send values back into the yield inside the
generator. When I want to use the generator, though, I have to
essentially duplicate the machinery of a "for" loop, because the "for"
loop does not have a mechanism to send into the generator. Here is a
toy example:

def TestGen1():
    for i in xrange(3):
        sendval = yield i
        print "   got %s in TestGen()" % sendval

g = TestGen1()
sendval = None
try:
    while True:
        val = g.send(sendval)
        print 'val in "while" loop %d' % val
        sendval = val * 10
except StopIteration: pass

I have to explicitly create the generator with an assignment, send an
initial None to the generator on the first go, then have to catch the
StopIteration exception. In other words, replicate the "for"
mechanism, but use send() instead of next().

It would be nice if I could just do this instead:

for val in TestGen1():
    print 'val in "for" loop %d' % val
    continue(val*10)

...or something similar. Is this an old idea? Has it been shot down in
the past already? Or is it worth pursuing? I Googled around and saw
one hit here: http://mail.python.org/pipermail/python-ideas/2009-February/003111.html,
but not much follow-up.

I wonder if people want to keep the idea of an "iterator" style
generator (where send() is not used) separate from the idea of a "co-
routine" style generator (where send() is used). Maybe combining the
two idioms in this way would cause confusion?

What do folks think?

dale