CODEWITHSUNDEEP
pythonbinaryhex
DigiAngel
DigiAngel

Reputation: 5

Assist with Python 3, hex, and addition

First time python app, so of course it's not been easy ;) In plain English this is what I'm trying to do:

read a binary file in, if any bytes are 0x00 change them to 0xFF, otherwise add 0x01 to each byte and write to a new file.

So there it is..my hope is something like

./convert.py file1.bin file2.bin

Here's what I have so far:

#!/usr/bin/env python3
import sys
with open(sys.argv[1], "rb") as f:
        byte = f.read(1)
        while byte:
                # Do stuff with byte.
                if byte = b'\x00'
                        byte = b'\xFF'
                else
                        byte = byte + b'\x01'
                byte = f.read(1)

but that's all I have so far...clearly this is very broken. I figured this would be a good learning opportunity...thanks for any assistance you might be able to give.

Upvotes: 0

Views: 849

Answers (1)

Doron Cohen
Doron Cohen

Reputation: 1046

First, you have a bug in the if byte = b'\x00' line, you meant ==. This is one of the most dangerous bugs in software development and that's why python doesn't allow assignment inside a condition. Second, better check for the length of byte because python reads bytes from file as a list of bytes. So, in the end of the file you will get an empty list of bytes.

Now for the code:

#!/usr/bin/env python3
import sys

with open(sys.argv[1], "rb") as fin, open(sys.argv[2], "wb") as fout:
        byte = fin.read(1)
        while len(byte):
                # Do stuff with byte.
                if byte == b'\x00'
                        byte = b'\xFF'
                else
                        byte = bytes((ord(byte) - 1,))
                fout.write(byte)
                byte = fin.read(1)

Upvotes: 1

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