title: How to reproduce the default sklearn CountVectorizer tokenization with only regex?
body: <p>I don't want to use <code>CountVectorizer</code> but try to reproduce it's tokenizing. I know it removes some special characters and puts them in lower case. I tried this regex <code>r'[\W_]+'</code> and is having <code>' '</code> as delimiter but still I'm not able to reproduce it. Any ideas?</p>