Build a “what changed_” file comparison tool

Here’s a complete implementation of a simple “What Changed?” file comparison tool in Python. This tool takes two files as input, compares their contents line by line, and outputs a clear difference report. It supports added, removed, and modified lines.

python
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import difflib
import sys
import argparse


def read_file(filepath):
    with open(filepath, 'r', encoding='utf-8') as file:
        return file.readlines()


def compare_files(file1_lines, file2_lines, file1_name="File1", file2_name="File2"):
    diff = difflib.unified_diff(
        file1_lines, file2_lines,
        fromfile=file1_name,
        tofile=file2_name,
        lineterm=''
    )
    return list(diff)


def highlight_changes(diff_lines):
    for line in diff_lines:
        if line.startswith('+') and not line.startswith('+++'):
            print(f"33[92m{line}33[0m")  # Green for additions
        elif line.startswith('-') and not line.startswith('---'):
            print(f"33[91m{line}33[0m")  # Red for deletions
        else:
            print(line)


def main(file1_path, file2_path):
    file1_lines = read_file(file1_path)
    file2_lines = read_file(file2_path)

    diff = compare_files(file1_lines, file2_lines, file1_path, file2_path)

    if not diff:
        print("No changes detected.")
    else:
        print("Changes found:n")
        highlight_changes(diff)


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description="Compare two text files and highlight differences.")
    parser.add_argument("file1", help="Path to the original file")
    parser.add_argument("file2", help="Path to the updated file")

    args = parser.parse_args()

    main(args.file1, args.file2)

Features

• Uses difflib.unified_diff to show changes in Unix diff style.

• Highlights additions in green and deletions in red in the terminal using ANSI escape codes.

• Displays file names and change context.

Usage

1. Save this script as what_changed.py.

2. Run it from the command line:

bash
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python what_changed.py old_version.txt new_version.txt

Optional Enhancements

• Add support for side-by-side comparison.

• Include GUI support using Tkinter or a web interface.

• Add word-level difference detection using difflib.ndiff().

Let me know if you want a version that runs in the browser or as a web app.