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Date: Fri, 17 Feb 2012 11:05:23 -0800
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Subject: Re: signed to unsigned
From: Chris Rebert <clp2@rebertia.com>
To: Brad Tilley <kj4eit@gmail.com>
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On Fri, Feb 17, 2012 at 10:51 AM, Brad Tilley <kj4eit@gmail.com> wrote:
> In C or C++, I can do this for integer conversion:
>
> unsigned int j =3D -327681234; // Notice this is signed.
>
> j will equal 3967286062. I thought with Python that I could use struct
> to pack the signed int as an unsigned int, but that fails:
>
>>>> x =3D struct.pack("<I", -327681234)
> Traceback (most recent call last):
> =C2=A0File "<stdin>", line 1, in <module>
> struct.error: integer out of range for 'I' format code
>
> Is there an easy way in Python to do the same conversion that C or C++
> code does? Thanks for any advice.

Pack it as the actual type, then unpack it as the desired type:

Python 2.7.1 (r271:86832, Jul 31 2011, 19:30:53)
Type "help", "copyright", "credits" or "license" for more information.
>>> from struct import pack, unpack
>>> unpack('=3DI', pack('=3Di',-327681234))
(3967286062,)

I would think there's some more efficient way to do this though.

Cheers,
Chris