How to add hex bytes in a string?

Question

I have this string of hex bytes, separated by spaces:

byteString = "7E 00 0A 01 01 50 01 00 48 65 6C 6C 6F"

How to add bytes in this way:

01 + 01 + 50 + 01 + 00 + 48 + 65 + 6C + 6C + 6F = 247

How is the original set of bytes stored? In a list of integers, a single string, etc? — Rhumborl, Feb 29 '20 at 13:36
Does this answer your question? [hexadecimal string to byte array in python](https://stackoverflow.com/questions/5649407/hexadecimal-string-to-byte-array-in-python) — Rhumborl, Feb 29 '20 at 13:42
there is a conversion of hexadecimal string to byte array. There is no addition. — thomas, Feb 29 '20 at 13:51
@thomas ***"there is a conversion"***: First you have cast, then you can add. You can't do math's with string objects. — stovfl, Feb 29 '20 at 14:01

CristiFati · Accepted Answer · 2020-02-29T16:05:36.410

Considering that you have the hex sequence as a str (bytes), what you need to do is:

Split the sequence in smaller strings each representing a byte (2 hex digits): "7E", "00", ...
Convert each such string to the integer value corresponding to the hex representation (the result will be a list of integers)
Add the desired values (ignoring the 1^st 3)

>>> byte_string = "7E 00 0A 01 01 50 01 00 48 65 6C 6C 6F"
>>>
>>> l = [int(i, 16) for i in byte_string.split(" ")]  # Split and conversion to int done in one step
>>> l
[126, 0, 10, 1, 1, 80, 1, 0, 72, 101, 108, 108, 111]
>>>
>>> [hex(i) for i in l]  # The hex representation of each element (for checking only)
['0x7e', '0x0', '0xa', '0x1', '0x1', '0x50', '0x1', '0x0', '0x48', '0x65', '0x6c', '0x6c', '0x6f']
>>>
>>> s = sum(l[3:])
>>>
>>> s
583
>>> hex(s)
'0x247'

score 0 · Answer 2 · answered Feb 29 '20 at 14:09

You need to tackle this in 2 parts - convert the string to a list of numbers, then sum the list. For this you can use the built-in bytearray.fromhex and sum functions:

byteString = "7E 00 0A 01 01 50 01 00 48 65 6C 6C 6F"
numberList = bytearray.fromhex(byteString)
total = sum(numberList)

How to add hex bytes in a string?

2 Answers2