Hex string to signed int in Python 3.2?

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How do I convert a hex string to a signed int in Python 3.2?

The best I can come up with is

h = '9DA92DAB'
b = bytes(h, 'utf-8')
ba = binascii.a2b_hex(b)
print(int.from_bytes(ba, byteorder='big', signed=True))

Is there a simpler way? Unsigned is so much easier: int(h, 16)

BTW, the origin of the question is itunes persistent id - music library xml version and iTunes hex version

hex integer python-3.x
5 Answers

It's a very late answer, but here's a function to do the above. This will extend for whatever length you provide. Credit for portions of this to another SO answer (I lost the link, so please provide it if you find it).

def hex_to_signed(source):
    """Convert a string hex value to a signed hexidecimal value.

    This assumes that source is the proper length, and the sign bit
    is the first bit in the first byte of the correct length.

    hex_to_signed("F") should return -1.
    hex_to_signed("0F") should return 15.
    """
    if not isinstance(source, str):
        raise ValueError("string type required")
    if 0 == len(source):
        raise valueError("string is empty")
    sign_bit_mask = 1 << (len(source)*4-1)
    other_bits_mask = sign_bit_mask - 1
    value = int(source, 16)
    return -(value & sign_bit_mask) | (value & other_bits_mask)
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