Compare disk images block-by-block, print out index of sectors with changes and save the different blocks to file

pydiskcomp.py

import os

afile = "sdcard.img"
bfile = "sdcard.img.manualworks"

afilediff = "sdcard.img.diff"
bfilediff = "sdcard.img.manualworks.diff"

afile_size = os.path.getsize(afile)
bfile_size = os.path.getsize(bfile)

if afile_size != bfile_size:
    raise "different sizes!"

incident = 0
with open(afile, 'rb') as af:
    with open(bfile, 'rb') as bf:
        pos = 0
        while(pos < afile_size):
            pos = af.tell()
            a_sect = af.read(512)
            b_sect = bf.read(512)


            if (a_sect != b_sect):
                print(f"different data at byte {pos} (sector {pos/512})")
                print("a_file")
                print(str(a_sect))
                print("b_file")
                print(str(b_sect))
                print()

                with open(f"afilediff-{incident}", 'wb') as afd:
                    afd.write(a_sect)
                with open(f"bfilediff-{incident}", 'wb') as bfd:
                    bfd.write(b_sect)

                incident += 1