如何在MxNet中计算n-gram?

我想在MxNet中对一组字符串进行N-gram。当然,我会这样做 TFIDF Vectorizing

def tfidf(str_list, ngram_width=3):
    tf = {}
    for s in str_list:
        for start, end in zip(range(len(s) - ngram_width),
                              range(ngram_width, len(s))):
            if s[start:end] not in tf:
                tf[s[start:end]] = 0
            tf[s[start:end]] += 1

    idf = {}
    for t in tf.keys():
        cnt = 0
        for s in str_list:
            if t in s:
                cnt += 1
            idf[t] = len(str_list)/(cnt + 1.0)

    return {t:tf[t]*idf[t] for t in tf.keys()}