def write_text(filename, data, add=False):
    """ Write image data to text file

    :param filename: name of text file to write data to
    :type filename: str
    :param data: image data to write to text file
    :type data: numpy array
    :param add: whether to append to existing file or not. Default is `False`
    :type add: bool
    """
    write_type = 'a' if add else 'w'
    with open(filename, write_type) as file:
        print(data, end='', file=file)
