Python NLTK: Bigrams trigrams fourgrams

Question

I have this example and i want to know how to get this result. I have text and I tokenize it then I collect the bigram and trigram and fourgram like that

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Answer 1

I do it like this:

def words_to_ngrams(words, n, sep=" "):
    return [sep.join(words[i:i+n]) for i in range(len(words)-n+1)]

This takes a list of words as input and returns a list of ngrams (for given n), separated by sep (in this case a space).