Copy files from Folder A to C if not present in B (Python >=3.2)

copy_unique.py

import os
import shutil
import argparse


def copy_unique_files(folder_a: str, folder_b: str, folder_c: str, recursive: bool = False) -> None:
    """Copy files from folder_a to folder_c if they do not exist in folder_b."""
    os.makedirs(folder_c, exist_ok=True)

    if recursive:
        files_in_b = {
            os.path.relpath(os.path.join(root, f), folder_b)
            for root, _, files in os.walk(folder_b)
            for f in files
        }
        for root, _, files in os.walk(folder_a):
            rel_dir = os.path.relpath(root, folder_a)
            dest_dir = os.path.join(folder_c, rel_dir)
            os.makedirs(dest_dir, exist_ok=True)

            for f in files:
                rel_path = os.path.join(rel_dir, f)
                src_path = os.path.join(root, f)
                dest_path = os.path.join(dest_dir, f)

                if rel_path not in files_in_b:
                    shutil.copy2(src_path, dest_path)
                    print(f"Copied: {rel_path}")
                else:
                    print(f"Skipped: {rel_path}")
    else:
        files_in_b = set(os.listdir(folder_b))
        for f in os.listdir(folder_a):
            src_path = os.path.join(folder_a, f)
            dest_path = os.path.join(folder_c, f)
            if os.path.isfile(src_path) and f not in files_in_b:
                shutil.copy2(src_path, dest_path)
                print(f"Copied: {f}")
            else:
                print(f"Skipped: {f}")

    print("\n✅ Copy operation complete.")


def main():
    parser = argparse.ArgumentParser(
        description="Copy files from folder A to folder C if they don't exist in folder B."
    )
    parser.add_argument("folder_a", help="Source folder (A)")
    parser.add_argument("folder_b", help="Comparison folder (B)")
    parser.add_argument("folder_c", help="Destination folder (C)")
    parser.add_argument(
        "-r", "--recursive", action="store_true", help="Enable recursive mode (include subfolders)"
    )
    args = parser.parse_args()

    copy_unique_files(args.folder_a, args.folder_b, args.folder_c, args.recursive)

# importable pattern
if __name__ == "__main__":
    main()