texts=[[word for word in document.lower().split() if word not in stoplist] for document in documents]
这段代码等同于：
texts=[]
for document in documents:
words=[]
for word in document.lower().split():
if word not in stoplist():
words.append(word)
texts.append(words)
原文：https://www.cnblogs.com/zyber/p/9594051.html