It is vital for me and any other monk who may wish to comment on your code to know the structure of the data you are trying to parse with the code. Without a clear definition of this structure, we're just guessing. One important point to make clear is if you are trying to parse raw binary data, or if the data is in some form such as, literally, '1A2B334566778B9A' as is suggested by your use of the 'H' unpack specifier.