['/link_body.html', 'http://domain.com/link_body.html']

>>> urllib.basejoin('http://abc', '/def')
'http://abc/def'
>>> urllib.basejoin('http://abc', 'def')
'http://abc/def'
>>>

>>> 'http://site'.startswith('http://')
True
>>> '/site'.startswith('http://')
False
>>>