BeautifulSoup庫未寫明解析器警告

from urllib.request import urlopen
from bs4 import BeautifulSoup
html = urlopen("http://www.pythonscraping.com/pages/page1.html")
bsObj = BeautifulSoup(html.read())
print(bsObj.h2)

代碼運行之后警告如下：
UserWarning: No parser was explicitly specified, so I'm using the best available HTML parser for this system ("lxml"). This usually isn't a problem, but if you run this code on another system, or in a different virtual environment, it may use a different parser and behave differently.

The code that caused this warning is on line 4 of the file D:/Python/venv/test8.py. To get rid of this warning, pass the additional argument 'features="lxml"' to the BeautifulSoup constructor.

翻譯如下：
用戶警告：沒有顯式指定語法分析器，因此我使用了此系統(tǒng)的最佳可用HTML語法分析器（“l(fā)xml”）。這通常不是問題，但是如果您在另一個系統(tǒng)上運行此代碼，或者在不同的虛擬環(huán)境中運行此代碼，它可能會使用不同的解析器并表現(xiàn)出不同的行為。

導致此警告的代碼位于文件d:/python/venv/test8.py的第4行。要消除此警告，請將附加參數(shù)'features=“l(fā)xml”'傳遞給beautifulsoup構造函數(shù)。

解決：指定解析器，一般使用'lxml'

from urllib.request import urlopen
from bs4 import BeautifulSoup
html = urlopen("http://www.pythonscraping.com/pages/page1.html")
bsObj = BeautifulSoup(html.read(),'lxml')
print(bsObj.h2)