[Python-Dev] switching on -3 from within a program?

Benjamin Peterson musiccomposition at gmail.com
Tue Sep 16 22:45:45 CEST 2008

On Tue, Sep 16, 2008 at 10:32 AM, Anthon van der Neut
<avanderneut at avid.com> wrote:
> With a minor modification to the Makefile I was able to get mod_wsgi
> v2.3 to work with python2.6rc1.
> I promptly got a warning in my apache log files on the depcrecated use
> of 'sha' in the paste's cookie module, good! And easily fixed.
> After that I was looking for a way to switch on the -3 warnings from
> within my code to have extra warnings show up in my apache log file.
> After reading some documentation I tried from the python2.6 prompt:
> import sys
> sys.py3kwarning = True
> x = { 'abc': 1 }; x.has_key('abc')
> which does not give a warning (starting python2.6 with the -3 option of
> course does).
> Is there anyway to switch this on from within a program with a Python
> statement?
> If not, would I need to make a small C-extension module (to be imported
> as the first module) that sets Py_Py3WarningFlag or something else at
> the C level, or would that better be done by mod_wsgi's C code.

You could also utilize a nifty ctypes trick:

import ctypes

def engage_py3k_warning():
     flag = ctypes.c_int.in_dll(ctypes.pythonapi, "Py_Py3kWarningFlag")
     flag.value = 1

Benjamin Peterson
"There's no place like"

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