python generator

>>> lst_num = [1,2,3]
>>> iter = (i for i in lst_num)
>>> print iter.next
<method-wrapper 'next' of generator object at 0xb71566e4>
>>> print iter.next()
1
>>> print iter.next()
2
>>> print iter.next()
3
>>> print iter.next()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration

 

>>> def use_yield():
...    for i in range(10):
...      yield(i)
...
>>>
>>> iter = use_yield()
>>> iter.next()
0
>>> iter.next()
1
>>> iter.next()
2

 

>>> def use_send():
...   print 'how are you?',
...   m = yield('55555')
...   print m
...   n = yield('aaaaaaaaaaa')
...   print 'ok!'
...
>>> test = use_send()
>>> test.send(None)
how are you?
'55555'
>>> test.next()
None
'aaaaaaaaaaa'
>>> test.next()
ok!
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration
>>> test = use_send()
>>> test.next()
how are you?
'55555'
>>> test.send('fine,3Q.')
fine,3Q.
'aaaaaaaaaaa'

第一個例子是告訴怎麼輸出generator對象

第2個是使用 yield 產生generator對象

第3個例子涉及到generatorde 原理，

m = yield('55555')
相當於下面僞代碼
print(‘55555’)       //輸出55555m = wait_and get()   //等待輸入，並把值返給m,另外告訴next() = send(None)

詳細解釋參考http://blog.donews.com/limodou/archive/2006/09/04/1028747.aspx