def count_non_ascii_chars(file_path: str) -> int:
    """Counts non ascii characters and returns their amount.

    Args:
        file_path: the pathname (absolute or relative to the current working directory)
        of the file to be opened.

    Returns:
        amount of non ascii characters.

    """
    amount = 0
    with open(file_path, encoding="unicode-escape") as file:
        for line in file:
            for symbol in line:
                if not symbol.isascii():
                    amount += 1
    return amount