def get_file_size(filename):
    """
    Get the file size of a given file

    :param filename: string: pathname of a file
    :return: human readable filesize
    """
    if os.path.isfile(filename):
        return convert_size(os.path.getsize(filename))
    return None
Get the file size of a given file

    :param filename: string: pathname of a file
    :return: human readable filesize