def consumer():
 r = 'yield'
 while True:
  #当下边语句执行时，先执行yield r，然后consumer暂停，此时赋值运算还未进行
  #等到producer调用send()时，send()的参数作为yield r表达式的值赋给等号左边
  n = yield r #yield表达式可以接收send()发出的参数
  if not n:
   return
  print('[CONSUMER] Consuming %s...' % n)
  r = '200 OK'

def produce(c):
 c.send(None)
 n = 0
 while n < 5:
  n = n + 1
  print('[PRODUCER] Producing %s...' % n)
  r = c.send(n) #调用consumer生成器
  print('[PRODUCER] Consumer return: %s' % r)
 c.close()

c = consumer()
produce(c)

def gen():
 a = yield 1
 print('yield a % s' % a)
 b = yield 2
 print('yield b % s' % b)
 c = yield 3
 print('yield c % s' % c)


r = gen()
x = next(r)
print('next x %s' % x)
y = r.send(10)
print('next y %s' %y)
z = next(r)
print('next z %s' % z)