How to convert network hex string to integer in python

Question

I have a hexadecimal string which I have received from internet (SSL client). It is as follows: "\x7f\xab\xff". This string is actually the length of something. I need to calculate the integer value of a sub-string in the above string (based on starting and ending position). How do I do that.

I tried struct.pack and unpack. It did not work I tried doing a split based on \x, and that gave some UTF error I tried converting the string to a raw string. Even that did not work

    r"\xff\x7f".replace('\x' , '')

    SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in 
    position 0-1: truncated \xXX escape


    >>> "\xff\x7f"[1]   
    '\x7f'
    >>> "\xff\x7f"[0]   
    'ÿ'


    >>> "\xff\x7f"[1]
    '\x7f'
    >>> "\xff\x7f"[0]   
    'ÿ'

Answer 1

The following worked for me:

>>> str_val = r'\xff\x7f'
>>> int_val = int(str_val.replace('\\x', ''), 16)
>>> int_val
65407

Don't forget that the backslash character is literally appearing in the string. So to target it, you need to declare '\\x' , not just '\x' !

Note that this also assumes the 1st octet, '\xff', is higher/more significant than the second, '\x7f'. It's possible the source of this value wants you to treat the second value as the more significant one.