A script to rename all media files in a given directory to one more suitable for Plex Media Server

massrename.py

"""os, for file IO"""
import os
import re
import argparse


def files(path):
    """ Returns a list of filenames from the given directory.
    https://stackoverflow.com/questions/14176166/list-only-files-in-a-directory
    """
    for file in os.listdir(path):
        if os.path.isfile(os.path.join(path, file)):
            yield file  # filename as string


def build_associations_dictionary(filenames):
    """Builds a dictionary from a list of filenames.
    The keys are the season and episode identifying strings.
    example: {"S01E01":"/path/to/title.S01E01.mp4"}
    """
    number_regex = r"s\d{1,2}e\d{1,2}"
    compiled_number_regex = re.compile(
        number_regex, re.MULTILINE | re.IGNORECASE)
    associations = {}
    for filename in filenames:
        episode_search = compiled_number_regex.findall(filename)
        if episode_search:
            associations[episode_search[0]] = filename
    return associations


def get_args():
    """Sets up command-line arguments. Returns the parsed arguments."""
    parser = argparse.ArgumentParser()
    parser.add_argument("directory",
                        type=str,
                        help="The directory containing the media files to be renamed. Ignores trailing slahes.")
    parser.add_argument("title",
                        type=str,
                        help="The title of the media to be renamed.")
    args = parser.parse_args()
    return args


def main():
    """The primary or controlling function."""
    args = get_args()
    working_directory = os.path.abspath(args.directory)
    if not os.path.isdir(working_directory):
        print("The path provided is not a directory.")
        exit()
    files_in_directory = [file for file in files(working_directory)]
    media_associations = build_associations_dictionary(files_in_directory)
    for key in media_associations:
        title = args.title
        episode_identifier = key
        old_filename = media_associations[key]
        _, file_extension = os.path.splitext(old_filename)
        new_filename = f"{title} {episode_identifier}{file_extension}"
        new_filepath = os.path.join(args.directory, new_filename)
        old_filepath = os.path.join(args.directory, old_filename)
        os.rename(old_filepath, new_filepath)


if __name__ == "__main__":
    main()

Moved the regex inside the only function that uses it.