hex to bin 16 bit word

Is there an other way to do this?

What to decode hex '0xC0A8'  and return signed short int.

>>> struct.unpack('>h','\xC0\xA8')
(-16216,)


Above works just wondering if there is cleaner way without writing a
function.

Bill
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[Paul Rubin-7]

python <[hidden email]> writes:
> What to decode hex '0xC0A8'  and return signed short int.

Is this right?

    n = int('0xC0A8', 16)
    if n >= 0xffff:
       n -= 0x10000
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[Steven D'Aprano-11]

On Fri, 27 Apr 2012 11:56:45 -0700, Paul Rubin wrote:

> python <[hidden email]> writes:
>> What to decode hex '0xC0A8'  and return signed short int.
>
> Is this right?
>
>     n = int('0xC0A8', 16)
>     if n >= 0xffff:
>        n -= 0x10000


No.

>>> struct.unpack('>h',b'\xC0\xA8')
(-16216,)
>>> n = int('0xC0A8', 16)
>>> if n >= 0xffff:
...     n -= 0x10000
...
>>> n
49320


Should be -16216.

Personally, I don't see why the OP doesn't just use struct.unpack to
unpack a struct.



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[Grant Edwards-7]

On 2012-04-27, Paul Rubin <[hidden email]> wrote:
> python <[hidden email]> writes:
>> What to decode hex '0xC0A8'  and return signed short int.
>
> Is this right?
>
>     n = int('0xC0A8', 16)
>     if n >= 0xffff:
>        n -= 0x10000

Yes, as long as the input value doesn't exceed 0x1ffff.  This is
probably better:

 n = int('0xc0a8'16) & 0xffff

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[Paul Rubin-7]

Steven D'Aprano <[hidden email]> writes:
>> Is this right?
>>
>>     n = int('0xC0A8', 16)
>>     if n >= 0xffff:
>>        n -= 0x10000
> No.

Oops, I meant n >= 0x7fff.  Checking the sign bit.  

Grant Edwards <[hidden email]> writes:
> Yes, as long as the input value doesn't exceed 0x1ffff.  This is
> probably better:
>
>  n = int('0xc0a8'16) & 0xffff

Yeah, I was relying on the specification that the input was 16 bits.
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[Ian Kelly-2]

On Fri, Apr 27, 2012 at 12:56 PM, Paul Rubin <[hidden email]> wrote:
> python <[hidden email]> writes:
>> What to decode hex '0xC0A8'  and return signed short int.
>
> Is this right?
>
>    n = int('0xC0A8', 16)
>    if n >= 0xffff:
>       n -= 0x10000

No.

n = int('0xC0A8', 16)
if n >= 0x8000:
    n -= 0x10000
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[MRAB-2]

On 27/04/2012 20:32, Ian Kelly wrote:

> On Fri, Apr 27, 2012 at 12:56 PM, Paul Rubin<[hidden email]>  wrote:
>>  python<[hidden email]>  writes:
>>>  What to decode hex '0xC0A8'  and return signed short int.
>>
>>  Is this right?
>>
>>      n = int('0xC0A8', 16)
>>      if n>= 0xffff:
>>         n -= 0x10000
>
> No.
>
> n = int('0xC0A8', 16)
> if n>= 0x8000:
>      n -= 0x10000

Or:

n = int('0xC0A8', 16)
n -= (n & 0x8000) * 2

:-)
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[Grant Edwards-7]

On 2012-04-27, Grant Edwards <[hidden email]> wrote:

> On 2012-04-27, Paul Rubin <[hidden email]> wrote:
>> python <[hidden email]> writes:
>>> What to decode hex '0xC0A8'  and return signed short int.
>>
>> Is this right?
>>
>>     n = int('0xC0A8', 16)
>>     if n >= 0xffff:
>>        n -= 0x10000
>
> Yes, as long as the input value doesn't exceed 0x1ffff.  This is
> probably better:
>
>  n = int('0xc0a8'16) & 0xffff

Oops, missed the "signed" part of the requirement.

   n = int('0xc0a8',16) & 0xffff
   
   if (n & 0x8000): n |= -1 & ~0xffff

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[Grant Edwards-7]

On 2012-04-27, Grant Edwards <[hidden email]> wrote:

> On 2012-04-27, Grant Edwards <[hidden email]> wrote:
>> On 2012-04-27, Paul Rubin <[hidden email]> wrote:
>>> python <[hidden email]> writes:
>>>> What to decode hex '0xC0A8'  and return signed short int.
>>>
>>> Is this right?
>>>
>>>     n = int('0xC0A8', 16)
>>>     if n >= 0xffff:
>>>        n -= 0x10000
>>
>> Yes, as long as the input value doesn't exceed 0x1ffff.  This is
>> probably better:
>>
>>  n = int('0xc0a8'16) & 0xffff
>
> Oops, missed the "signed" part of the requirement.
>
>    n = int('0xc0a8',16) & 0xffff
>    
>    if (n & 0x8000): n |= -1 & ~0xffff

or this:

     if (n & 0x8000): n = -((~n & 0x7fff) + 1)



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snip

Thanks for all you suggestions.

This was sent via email.  Original solution with struct was not
to bad but less clear that this was sent to me via email.

>>> import ctypes
>>> x = ctypes.c_int16(0xC08A)
>>> x.value
>>> -16246
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