Using urllib and BeautifulSoup to retrieve info from web with Python

I can get the html page using urllib, and use BeautifulSoup to parse the html page, and it looks like that I have to generate file to be read from BeautifulSoup.

import urllib                                       
sock = urllib.urlopen("http://SOMEWHERE") 
htmlSource = sock.read()                            
sock.close()                                        
--> write to file

Is there a way to call BeautifulSoup without generating file from urllib?