def split_long_sentence(sentence, words_per_line):
    """Takes a sentence and adds a newline every "words_per_line" words.

    Parameters
    ----------
    sentence: str
        Sentene to split
    words_per_line: double
        Add a newline every this many words
    """
    words = sentence.split(' ')
    split_sentence = ''
    for i in range(len(words)):
        split_sentence = split_sentence + words[i]
        if (i+1) % words_per_line == 0:
            split_sentence = split_sentence + '\n'
        elif i != len(words) - 1:
            split_sentence = split_sentence + " "
    return split_sentence