[Pythonmac-SIG] cyptes problem on MacOS X

Perry Smith pedz at easesoftware.com
Mon Dec 11 21:39:24 CET 2006


I don't use floats and double much.  But the printf man page implies  
that all
floats are actually passed as doubles.  I vaguely recall that to be  
the case.

But I doubt if the python thingy knows that.  Try not passing  
floats.  You might
also have problems trying to pass char's and short's (since they are  
promoted
to int's).

On Dec 11, 2006, at 2:20 PM, Russell E. Owen wrote:

> I've been trying out ctypes (from MacPython 2.5) on MacOS X on a  
> PPC Mac
> and have run into a problem. I hope I'm just doing something  
> stupid, but
> it seems to match the tutorial so I'm really puzzled:
>
> import ctypes
> libc = ctypes.CDLL("libc.dylib")
> libc.printf("int=%d float=%f double=%f\n", ctypes.c_int(1),
> ctypes.c_float(2.0), ctypes.c_double(3.0));
>
> results in:
> int=1 float=-1.996124 double=0.000000
>
> I realize the docs doesn't actually claim to handle dylib files, but
> I've seen at least some info on the web that claims it works. One site
> suggested the need for ctypes.RTLD_GLOBAL to CDLL but adding it  
> made no
> difference.
>
> On a related subject...assuming I can get this to work...does anyone
> have any idea how the speed of ctypes relates to programming a  
> python C
> extension or using SWIG? This is mostly for use with NumPy and
> interfacing python to C/C++-based heavy duty astronomical image
> processing code.
>
> Other suggestions are welcome. We'll mostly be interfacing to C++ so
> I've considered trying out Boost, but it hasn't had an update in years
> which worries me. Robustness, ease of use and speed are all major
> requirements. Linux and MacOS X are the main platforms.
>
> -- Russell
>
> _______________________________________________
> Pythonmac-SIG maillist  -  Pythonmac-SIG at python.org
> http://mail.python.org/mailman/listinfo/pythonmac-sig
>

Perry Smith ( pedz at easesoftware.com )
Ease Software, Inc. ( http://www.easesoftware.com )

Low cost SATA Disk Systems for IBMs p5, pSeries, and RS/6000 AIX systems


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