Mirror folder for utorrent

import argparse, os, errno

def main(sources, dest_folder, utorrent=False):
    """
    Script takes a list of paths (sources) and creates a matching links/folders
    hierarchy in a destination folder (dest_folder).

    You can include '*' in the sources to add everything in the current directory.
    """
    if utorrent:
        # utorrent behaves like this:
        # 1. single-file torrent: we'll receive the file and its parent dir (which probably contains all other downloads!!)
        # 2. dir-torrent: we'll only receive the folder containing the files.
        assert len(sources) == 2

        if '' in sources:
            # dir
            src = next(f for f in sources if f != '')
        else:
            # file
            src = next(f for f in sources if os.path.isfile(f))

        sources = [src]

    dest_folder = os.path.abspath(dest_folder)
    paths = set()
    for source in sources:
        if source == '*':
            # wildcard mode! grab everything in the current directory
            # ...except self and the destination; true story!
            current_filename = os.path.realpath(__file__)
            current_folder = os.getcwd()
            for source in walk(os.getcwd()):
                if source not in [current_filename, dest_folder, current_folder]:
                    print(source)
                    paths.add(source)
        else:
            assert os.path.exists(source), "File doesn't exist: " + source
            paths.add(os.path.abspath(source))

    # create the destination path
    skip_on_exists(lambda: os.makedirs(args.dest_folder))

    # all good, create the links & folders!
    for f in paths:
        mirror_path(f, args.dest_folder)

def mirror_path(path, dest_folder):
    """
    Mirrors path into dest_folder, according to these rules:
        path is a file: a link is created in dest_folder
        path is directory: a directory is created in dest_folder,
        then everything inside is mirrored too.
    """
    path = os.path.abspath(path)
    dest_folder = os.path.abspath(dest_folder)
    # ensure we have a base directory to work with
    skip_on_exists(lambda: os.makedirs(dest_folder))
    # compute the emplacement of the mirror item
    dest = os.path.join(dest_folder, os.path.basename(path))

    if os.path.isdir(path):
        # source is a directory: mirror it with a normal directory
        skip_on_exists(lambda: os.makedirs(dest))
        # now we'll go into that source and mirror all items within,
        # setting the destination to the directory we just created
        for p in walk(path):
            mirror_path(p, dest)
    else:
        # this is a file; just create a symlink!
        skip_on_exists(lambda: os.symlink(path, dest))

def walk(path):
    """
    Returns everything (files+dirs) in path as absolute paths.
    Non-recursive.
    """
    for dirpath, dirnames, filenames in os.walk(path):
        return [os.path.join(dirpath, path) for path in dirnames + filenames]

def skip_on_exists(action):
    """
    Performs callable (action), ignoring any OSError indicating that
    the resource already exists.
    """
    try:
        action()
    except OSError as err:
        if err.errno == errno.EEXIST:
            pass  # directory already exists
        else:
            raise


if __name__ == '__main__':
    """
    Process command-line arguments and call main()
    """
    parser = argparse.ArgumentParser()
    parser.add_argument('sources', nargs='+', help='the files or dirs to process')
    parser.add_argument('--dest_folder', required=True, help='the destination folder')
    parser.add_argument('--utorrent', action='store_true', help='when calling from utorrent\'s advanced properties, set this switch so that you can pass both %F and %D for all torrents. DO NOT use this outside utorrent or it will not process all your files correctly.')
    args = parser.parse_args()
    main(args.sources, args.dest_folder, args.utorrent)