举例详解Python中yield生成器的用法

> def mygenerator():
...  print 'start...'
...  yield 5
... 
> mygenerator()   //在此处调用,并没有打印出start...说明存在yield的函数没有被运行,即暂停
<generator object mygenerator at 0xb762502c>
> mygenerator().next()  //调用next()即可让函数运行.
start...
5
> 

> def mygenerator():
...  print 'start...'
...  yield 5
... 
> mygenerator()   //在此处调用,并没有打印出start...说明存在yield的函数没有被运行,即暂停
<generator object mygenerator at 0xb762502c>
> mygenerator().next()  //调用next()即可让函数运行.
start...
5
> 

> def fun():
...  print 'start...'
...  m = yield 5
...  print m
...  print 'middle...'
...  d = yield 12
...  print d
...  print 'end...'
... 
> m = fun()    //创建一个对象
> m.next()    //会使函数执行到下一个yield前
start...
5
> m.send('message')  //利用send()传递值
message     //send()传递进来的 
middle...
12
> m.next()
None      //可见next()返回值为空
end...
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
StopIteration

for i, task in enumerate(taskseq):
  ...
  try:
   put(task)
  except IOError:
   debug('could not put task on queue')
   break

import multiprocessing as mp
import itertools
import time


def g():
 for el in xrange(50):
  print el
  yield el

import os

def f(x):
 time.sleep(1)
 print str(os.getpid()) +" "+ str(x)
 return x * x

if __name__ == '__main__':
 pool = mp.Pool(processes=4)    # start 4 worker processes
 go = g()
 result = []
 N = 11
 while True:
  g2 = pool.imap(f, itertools.islice(go, N))
  if g2:
   for i in g2:
    result.append(i)
    time.sleep(1)
  else:
   break
 print(result)