On Apr 17, 3:59 pm, Dale Roberts <goobe...@gmail.com> wrote: > 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
You can do it with a wrapping generator. I'm not sure if it interferes with your needs. It calls 'next' the first time, then just calls 'send' on the parameter with the value you send it. >>> def genf( ): ... x= True ... for _ in range( 10 ): ... i= yield( x ) ... if i is None: ... i= not x ... x= i ... >>> def for_send( gen ): ... x= next( gen ) ... while 1: ... x= yield( x ) ... x= gen.send( x ) ... >>> a= for_send( genf( ) ) >>> i= 0 >>> for x in a: ... print( i, x ) ... i+= 1 ... if not i% 3: ... _= a.send( False ) ... 0 True 1 False 2 True 3 True 4 False 5 True 6 True 7 False As you can see, it skips a beat every third iteration as directed. -- http://mail.python.org/mailman/listinfo/python-list
