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why generator assigned to slice?

ana sanchez private at private.com
Thu Jan 6 08:44:08 EST 2011 
In <ig1u77$4iv$00$1 at news.t-online.com> Peter Otten <__peter__ at web.de> writes:

>ana sanchez wrote:

>> i found this when i read the source of a program in python:
>> 
>>         self.__chunks[start:end] = (chunk for i in xrange(start, end))

>> what utility has to assign a generator to a slice???  ?the *final
>> result* isn't the same as this?:
>> 
>>         self.__chunks[start:end] = [chunk for i in xrange(start, end)]

>Whoever used the first variant probably was hoping that it was either faster 
>or used less peak memory. I think the latter is wrong, and the former can 
>easily be checked:

>$ python -m timeit -s'chunk = "yadda"; chunks = range(100); start = 20; end 
>= 50' 'chunks[start:end] = (chunk for i in xrange(start, end))'
>100000 loops, best of 3: 9.02 usec per loop

>$ python -m timeit -s'chunk = "yadda"; chunks = range(100); start = 20; end 
>= 50' 'chunks[start:end] = [chunk for i in xrange(start, end)]'
>100000 loops, best of 3: 4.16 usec per loop

>$ python -m timeit -s'chunk = "yadda"; chunks = range(100); start = 20; end 
>= 50' 'chunks[start:end] = [chunk]*(end-start)'
>1000000 loops, best of 3: 1.02 usec per loop


peter thank you very much!!!  (i like very much the timing "miniscripts")

ana
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