Negative hex to int

[John Machin]

On 15/06/2006 9:24 AM, Wojciech Muła wrote:
> andreas.lydersen at gmail.com wrote:
>> The problem is negative values. If the unit returns the hex value 'e7',
>> it means -25, but python says it's 231:
>> ---------------------------
>>>>> int('e7', 16)
>> 231
>> ---------------------------
>>
>> Does anyone have a clue a to what I need to do?
> 
> def u2(x):
> 	if x & 0x80: # MSB set -> neg.
> 		return -((~x & 0xff) + 1)

Holy obfuscation, Batman!

> 	else:
> 		return x
> 		
>>>> u2(int('e7', 16))
> -25
>>>> u2(int('12', 16))
> 18
> 
> w.