How to convert decimal to 1's complement hexadecimal in python

Question

I need to figure out, in python, how to convert a signed decimal to hexadecimal using 1's complement for negative values. The example results I need to get are below:

0 becomes 0000,

65.5 becomes 0041

200 becomes 00c8

-200 becomes ff37

I can easily get the positive ones using hex(), but how do I do the conversions to get the correct values for negative numbers?

Answer 1

Your examples are wrong. With 6.55 you actually mean 65 which leads to 0x41 . 20 becomes 0x14 , not 0xc8 because that would be 200 . The one complement for 0x20 is 0xeb not 0x37 or 0xff37 .

To calculate the one's-complement you can use the XOR-operator . Use 0xFF or 0xFFFF , depending on the bit-depth of your expected data.

16-Bit:

hex(0x14 ^ 0xFFFF) -> 0xffeb

0b0000000000010100 ^
0b1111111111111111
------------------
0b1111111111101011 -> 0xffeb

8-Bit:

hex(0x14 ^ 0xFF)   -> 0xeb