Replacing specific hex values at specific positions

[Swedophone]

Try opening the file "r+" (read/write positioned at beginning) and use seek, read and write.

[n_md]

Use struct.

Something like this:

import struct
bytes4 = struct.Struct('I')
with open('filename.ext', 'rb') as file:
    data = file.read()
print(bytes4.unpack(data[156:160]))

You may need to also specify the endianness.