Use yield to implement coroutine

gistfile1.py

def coroutine(func):
        def start(*args, **kwargs):
                cr = func(*args, **kwargs)
                cr.next()
                return cr
        return start

@coroutine
def grep(pattern):
        print "looking for %s" % pattern
        while True:
                line = (yield)
                if pattern in line:
                        print line

g = grep("python")
g.send("yeah, but no")
g.send("python test")
g.close()