python报错bs4.FeatureNotFound: Couldn't find a tree builder with the features you requested: lxml.

qpython运行

原代码：    soup = BeautifulSoup(r.text,'lxml')

报错：bs4.FeatureNotFound: Couldn't find a tree builder with the features you requested: lxml. Do you need to install a parser library?

改成：    soup = BeautifulSoup(r.text,'html.parser')

ok