how to convert negative integer value to hex in python

Question

I use python 2.6

>>> hex(-199703103)
\'-0xbe73a3f\'

>>> hex(199703103)
\'0xbe73a3f\'

Positive and negative value are the

Answer 1

Because Python integers are arbitrarily large, you have to mask the values to limit conversion to the number of bits you want for your 2s complement representation.

>>> hex(-199703103 & (2**32-1)) # 32-bit
'0xf418c5c1L'
>>> hex(-199703103 & (2**64-1)) # 64-bit
'0xfffffffff418c5c1L'

Python displays the simple case of hex(-199703103) as a negative hex value (-0xbe73a3f) because the 2s complement representation would have an infinite number of Fs in front of it for an arbitrary precision number. The mask value (2**32-1 == 0xFFFFFFFF) limits this:

FFF...FFFFFFFFFFFFFFFFFFFFFFFFF418c5c1
&                             FFFFFFFF
--------------------------------------
                              F418c5c1