How can Python compare the differences between two files?

To compare the differences between two files, you can use the following steps:

1. Open two files and read their contents line by line.
2. Store the content of each file in two distinct lists.
3. Compare these two lists using the SequenceMatcher class in the difflib module.
4. Use the get_opcodes() method to obtain a list of opcodes that describe how to convert one list into another.
5. Traverse through the list of operation codes and examine the type of each operation code.
6. If the type of operation code is ‘replace’, it means that the two files are different on that line.
7. If the opcode type is ‘delete’, it means that the first file has additional content on that line.
8. If the opcode type is ‘insert’, it means that the second file has additional content on that line.
9. Print out different lines and save them to a new file.

Here is a sample code:

import difflib

def compare_files(file1, file2, output_file):
    with open(file1, 'r') as f1, open(file2, 'r') as f2:
        lines1 = f1.readlines()
        lines2 = f2.readlines()

    differ = difflib.SequenceMatcher(None, lines1, lines2)
    opcodes = differ.get_opcodes()

    with open(output_file, 'w') as output:
        for opcode, start1, end1, start2, end2 in opcodes:
            if opcode == 'replace':
                output.write(f'Different line in file1: {lines1[start1:end1]}')
                output.write(f'Different line in file2: {lines2[start2:end2]}')
            elif opcode == 'delete':
                output.write(f'Extra line in file1: {lines1[start1:end1]}')
            elif opcode == 'insert':
                output.write(f'Extra line in file2: {lines2[start2:end2]}')

file1 = 'file1.txt'
file2 = 'file2.txt'
output_file = 'diff.txt'

compare_files(file1, file2, output_file)

The code above compares the content of two files, file1.txt and file2.txt, and saves the different lines in a file called diff.txt. You can modify the file names and paths as needed.