inverse of izip

[Satchidanand Haridas]

Hi,

How about using iter() to get another solution like the following:

 >>> starzip2 = lambda it: tuple([iter(x) for x in itertools.izip(*it)])

 >>> l,m = starzip2(itertools.izip(range(10),range(10)))

 >>> l
<tupleiterator object at 0x4016802c>
 >>> m
<tupleiterator object at 0x4016896c>

 >>> list(l)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
 >>> list(m)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Thanks,

Satchit

----
Satchidanand Haridas (sharidas at zeomega dot com)

ZeOmega (www.zeomega.com)
Open  Minds' Open Solutions

#20,Rajalakshmi Plaza,
South End Road,
Basavanagudi,
Bangalore-560 004, India



Steven Bethard wrote:

>Steven Bethard <steven.bethard <at> gmail.com> writes:
>  
>
>>What's the inverse of izip?  Of course, I could use zip(*) or izip(*),
>>e.g.:
>>
>>    
>>
>>>>>zip(*itertools.izip(range(10), range(10)))
>>>>>          
>>>>>
>>[(0, 1, 2, 3, 4, 5, 6, 7, 8, 9), (0, 1, 2, 3, 4, 5, 6, 7, 8, 9)]
>>    
>>
>>>>>x, y = itertools.izip(*itertools.izip(range(10), range(10)))
>>>>>x, y
>>>>>          
>>>>>
>>((0, 1, 2, 3, 4, 5, 6, 7, 8, 9), (0, 1, 2, 3, 4, 5, 6, 7, 8, 9))
>>
>>But then I get a pair of tuples, not a pair of iterators.  Basically,
>>I want to convert an iterator of tuples into a tuple of iterators.
>>    
>>
>
>Sorry to respond to myself, but after playing around with itertools for a 
>while, this seems to work:
>
>  
>
>>>>import itertools
>>>>starzip = lambda iterables: ((tuple[i] for tuple in itr) for i, itr in 
>>>>        
>>>>
>enumerate(itertools.tee(iterables)))
>  
>
>>>>starzip(itertools.izip(range(10), range(10)))
>>>>        
>>>>
><generator object at 0x008DED28>
>  
>
>>>>x, y = starzip(itertools.izip(range(10), range(10)))
>>>>x
>>>>        
>>>>
><generator object at 0x008E1058>
>  
>
>>>>y
>>>>        
>>>>
><generator object at 0x008E1080>
>  
>
>>>>list(x)
>>>>        
>>>>
>[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>  
>
>>>>list(y)
>>>>        
>>>>
>[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>
>Seems like a bit of work for the inverse of izip though so I'll wait to see if 
>anyone else has a better solution.  (Not to mention, it wouldn't be a single 
>line solution if I wasn't using 2.4...)
>
>Steve
>
>
>  
>