请教用 BeautifulSoup 包抓取链接的问题

下面的代码，用于搜索维基百科上凯文·贝肯词条里所有指向其他词条的链接。
搜索结果中那些指向其它词条页面的链接应具有如下特点：
• 它们都在 id 是 bodyContent 的 div 标签里
• URL 链接不包含分号
• URL 链接都以 /wiki/ 开头

代码如下：

from urllib.request import urlopen 
from bs4 import BeautifulSoup 
import datetime 
import random 
import re 
random.seed(datetime.datetime.now()) 
def getLinks(articleUrl): 
        html = urlopen(" https://en.wikipedia.org "+articleUrl) 
        bsObj = BeautifulSoup(html) 
        return bsObj.find("div", {"id":"bodyContent"}).findAll("a",href=re.compile("^(/wiki/)((?!:).)*$")) 
links = getLinks("/wiki/Kevin_Bacon")
print(links)

代码运行后报错如下，请问这是为什么呢？感谢指点！

Traceback (most recent call last):
  File "c:\Users\A\AppData\Roaming\Code\User\test\2.py", line 11, in <module>
    links = getLinks("/wiki/Kevin_Bacon")
  File "c:\Users\A\AppData\Roaming\Code\User\test\2.py", line 8, in getLinks
    html = urlopen(" https://en.wikipedia.org "+articleUrl)
  File "D:\Python\Python3\lib\urllib\request.py", line 223, in urlopen
    return opener.open(url, data, timeout)
  File "D:\Python\Python3\lib\urllib\request.py", line 526, in open
    response = self._open(req, data)
  File "D:\Python\Python3\lib\urllib\request.py", line 544, in _open
    '_open', req)
  File "D:\Python\Python3\lib\urllib\request.py", line 504, in _call_chain
    result = func(*args)
  File "D:\Python\Python3\lib\urllib\request.py", line 1361, in https_open
    context=self._context, check_hostname=self._check_hostname)
  File "D:\Python\Python3\lib\urllib\request.py", line 1320, in do_open
    raise URLError(err)
urllib.error.URLError: <urlopen error [Errno 11004] getaddrinfo failed>

saximi

2017-08-30 20:27:06 +08:00

程序是在 VSCODE 下执行的，去掉 URL 中的空格后程序报错如下。

如果把“ BeautifulSoup(html)”这句改为“ BeautifulSoup(html,'lxml')”则不会报错，但是从出错信息来看好像是没有明确指定一个 parser 导致的。

请问 parser 是什么？以及在 VSCODE 下如何设置才能做到明确指定 parser，从而让“ BeautifulSoup(html)”这句代码运行不出错呢?感谢指点！

D:\Python\Python3\lib\site-packages\bs4\__init__.py:181: 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 91 of the file C:\Users\A\.vscode\extensions\donjayamanne.python-0.7.0\pythonFiles\PythonTools\visualstudio_py_launcher.py. To get rid of this warning, change code that looks like this:
BeautifulSoup(YOUR_MARKUP})
to this:
BeautifulSoup(YOUR_MARKUP, "lxml")
markup_type=markup_type))