You don't need to manually save a page. Use urllib2 to get the html source you need:
from bs4 import BeautifulSoup
from urllib2 import urlopen
soup = BeautifulSoup(urlopen("http://my_site.com/mypage"))
Example:
>>> from bs4 import BeautifulSoup
>>> from urllib2 import urlopen
>>> soup = BeautifulSoup(urlopen('http://google.com'))
>>> soup('a')
[<a class="gb1" href="http://www.google.com/imghp?hl=en&tab=wi">Images</a>,
...
]