As per a thread on python-dev, I offered to add sys.iswow64process.  I'm
attaching a patch that does this (including news, docs and tests).  I'm
adding Martin to the nosy list as he has expressed reservations ("It
sounds like clutter of the sys module to me"), so I expect this to be
rejected.

I think this can be just as well done with (untested, as I don't have
access to a Windows system right now)

def iswow64():
    if platform.getarchitecture()[0] == '64-bit':return False
    return os.environ["PROCESSOR_ARCHITECTURE"] != "x86"

IOW, it's wow64 iff it's a 32-bit Python not running on an x86 machine.

I'm not sure if that is suggesting MS had no reason to add that API
function, or those reasons don't apply to users of Python, but as its
clear there is significant resistance I'm rejecting this report.

One reason for IsWow64Process is that it allows to determine the
wow-ness of a different process, which is e.g. needed to display the
asterisk in the process viewer. This reason indeed doesn't apply to
Python, and your patch doesn't expose that functionality.

Hi,

I am a Python user seeking an implementation of iswow64 and found this tracker. Unfortunately I don't think Martin's suggested alternative approach works.

os.environ["PROCESSOR_ARCHITECTURE"]

returns "x86" on my system when run from a 32-bit python, even though if I look at my "real" environment I see 

D:\>echo %PROCESSOR_ARCHITECTURE%
AMD64

i.e it appears that Windows is passing "false information", if you will, to whatever populates os.environ in 32-bit windows.

Perhaps Mark's patch should be resurrected. Or is there a further way to get this information?

[My Python version information:
D:\>python
ActivePython 2.6.5.12 (ActiveState Software Inc.) based on
Python 2.6.5 (r265:79063, Mar 20 2010, 14:22:52) [MSC v.1500 32 bit (Intel)] on win32
]

os.environ["PROCESSOR_ARCHITEW6432"] will tell you the true underlying processor architecture when under WOW. Therefore, if you find that this variable exists, you are under WOW.

Example, on my 64-bit machine with a 32-bit compiled Python:

Python 3.1.2 (r312:79149, Mar 21 2010, 00:41:52) [MSC v.1500 32 bit (Intel)] on
win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.environ["PROCESSOR_ARCHITECTURE"]
'x86'
>>> os.environ["PROCESSOR_ARCHITEW6432"]
'AMD64'

See also Issue7860.