Whether you're using yield-from or not, it doesn't seem to be possible to have a for-loop iterating over something that is also suspendable in a generator-based thread setting. The basic problem is that we have one channel and two different things we want to use it for. The obvious answer is that we need to multiplex. Since we're already using the entire bandwidth of the channel (anything could be a valid yielded value) we need to introduce some out-of-band data somehow. Suppose we have a new expression suspend [<value>] [with <tag>] This is a lot like a yield, except that it sends a tuple (value, tag). The existing yield expression yield <value> becomes equivalent to suspend <value> with 'yield' There is a new generator method to go along with this: g.resume(value, tag) If the generator is suspended at a suspend expression, the value of the suspend expression becomes (value, tag). If it is suspended at a yield, and the tag is 'yield' then the value becomes the value of the yield expression. (Not sure what to do in other cases, maybe raise an exception.) The existing send() method is mapped to resume() as follows: def send(self, value): value2, tag2 = self.resume(value, 'yield') if tag2 == 'yield': return value2 else: # What to do here? Ignore? Raise an exception? So we've generalised the yield channel into a suspend channel, which can have any number of sub-channels. We have reserved one of these sub-channels, tagged with 'yield', for carrying yielded values. The rest of the channels are free for use by other things such as thread-scheduling libraries. To complete this, we also need a variant of the for-loop that is willing to pass values from the other channels on to the caller. Picking a random syntax for illustration, for y from g(x): # body would be roughly equivalent to it = g(x) value = None tag = 'yield' try: while 1: value, tag = it.resume(value, tag) if tag == 'yield': y = value value = None # body else: value, tag = suspend value with tag except StopIteration: pass plus suitable handling of 'throw' and 'close'. -- Greg