CountVectorizer忽略大写

Question

CountVectorizer忽略大写单词的原因是什么？

cv = CountVectorizer(stop_words=None,analyzer='word',token_pattern='.*',max_features=None)
text = ['this','is','a','Test','!']
fcv = cv.fit_transform(list)
fcv = [cv.vocabulary_.get(t) for t in text]
print fcv

返回

[5, 3, 2, None, 1]

Answer 1

这是因为在CountVectorizer中，默认情况下lowercase设置为True，添加lowercase=False。

cv = CountVectorizer(stop_words=None, analyzer='word', token_pattern='.*',
        max_features=None, lowercase=False)