如何合併兩臺發電機？

Question

如何合併兩個不同的生成器，在每次迭代中，一個不同的生成器將獲得收益？

>>> gen = merge_generators_in_between("ABCD","12") 
>>> for val in gen: 
...  print val 
A 
1 
B 
2 
C 
D 

我該如何做到這一點？我在itertools中找不到它的功能。

Answer 1

照照itertools recipes下循環賽：

>>> from itertools import cycle, islice 
>>> def roundrobin(*iterables): 
     "roundrobin('ABC', 'D', 'EF') --> A D E B F C" 
     # Recipe credited to George Sakkis 
     pending = len(iterables) 
     nexts = cycle(iter(it).next for it in iterables) 
     while pending: 
      try: 
       for next in nexts: 
        yield next() 
      except StopIteration: 
       pending -= 1 
       nexts = cycle(islice(nexts, pending)) 


>>> for x in roundrobin("ABCD", "12"): 
     print x 


A 
1 
B 
2 
C 
D