def get_next_line_from_paragraph(paragraph, ll):
    """Return the largest substring from `paragraph` that ends in a space and
    doesn't exceed `ll`. Raise exception f no such string exists.
    """
    if paragraph[ll] is ' ':
        index = ll+1
    else:
        last_space = paragraph[:ll][::-1].find(' ')
        if last_space is -1:
            raise Exception("Word length exceeded line length")
        index = ll-last_space
    return paragraph[:index-1], paragraph[index:]