what is the difference between tfidf vectorizer and tfidf transformer

Question

I know that the formula for tfidf vectorizer is

Count of word/Total count * log(Number of documents / no.of documents where word is present)

I saw there's tfidf transformer in the scikit learn and I just wanted to difference between them. I could't find anything that's helpful.

Answer 1

TfidfVectorizer is used on raw documents, while TfidfTransformer is used on an existing count matrix, such as one returned by CountVectorizer