[SciPy-user] partially reading a file...

Travis E. Oliphant oliphant@enthought....
Wed Aug 6 13:14:35 CDT 2008


fred wrote:
> Travis E. Oliphant a écrit :
>
>   
>> Absolutely memory mapping still applies --- it's a perfect application 
>> for it.  But, you will probably need a 64-bit system.
>>     
> No problem.
>
>   
>> Memory mapping is how the OS handles "virtual memory" which uses disk 
>> space to increase main memory.  You are just using that idea directly 
>> with a memory mapped file.
>>     
> Ok.
> Thanks for the hint.
>
>   

More directly:

Use numpy.memmap --- look at the docstring for example use and help on 
all the arguments available.  But, something like this (untested):

a = numpy.memmap(<filename>, mode='r', dtype=float, shape=(nx,ny,nz))
b = a[:nx/4,:ny/4,:nz/4]
b.tofile(<somefilename>)

Should work...

-Travis




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