Python 32-bit on Windows 64-bit

MRAB python at
Fri Feb 11 19:27:36 EST 2011

On 11/02/2011 21:50, Sherm Pendley wrote:
> "Martin v. Loewis"<martin at>  writes:
>> Am 11.02.2011 19:41, schrieb Craig Yoshida:
>>> what kind of memory limitations to processes running on 32-bit python
>>> (with 32-bit C extensions like scipy) have on 64-bit Windows?   I'm
>>> having occasional MemoryErrors when running a python program on
>>> 64-bit Windows 7 that runs fine on my OS X machine.  Both machines
>>> are using a 64-bit OS and have 4GB of RAM.
>> In addition to the limitations Michel reports: on a 32-bit system,
>> objects are typically limited to using at most 2GiB, per object
>> (of course, you could have at most two objects that come close to
>> this size, since the whole address space would not be larger than
>> 4GiB).
> IIRC, 32-bit Windows programs are limited to 2GiB, reserving the rest
> of the virtual address space for Windows' own use.
It's possible to configure 32-bit Windows to allow up to 3GB user RAM.

> Also, 32-bit apps remain 32-bit, even if they're running on a 64-bit
> capable OS. Assuming you're running Snow Leopard on your Mac, you're
> using a 64-bit Python interpreter *and* a 64-bit OS. You need to have
> both to take advantage of a 64-bit memory space.

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