>>> ar = []
>>> ar.append(r.findall(url))
>>> ar
[['http://www.www.site.local']]
>>> ar.append(r.findall(url))
>>> ar
[['http://www.www.site.local'], ['http://www.www.site.local']]

>>> import lxml.html
>>> 
>>> doc = lxml.html.fromstring('<a href="http://www.domain.com">text</a>')
>>> lst = doc.xpath(r'//a/@href')
>>> lst
['http://www.domain.com']
>>>

>>> ar[0]
>>> ar[1]

>>> import re
>>> url='<a href="http://www.site2.local" target="_blank">http://www.site2.local</a><a href="http://www.site1.local" target="_blank">http://www.site1.local</a>'
>>> r = re.compile('(?<=href=").*?(?=")')
>>> ar=[]
>>> ar.append(r.findall(url))
>>> ar
[['http://www.site2.local', 'http://www.site1.local']]
>>> ar[0]
['http://www.site2.local', 'http://www.site1.local']
>>> ar[1]
Traceback (most recent call last):
  File "<pyshell#7>", line 1, in <module>
    ar[1]
IndexError: list index out of range

ar[0]

>>> ar
[['http://www.site2.local', 'http://www.site1.local']]
>>> ar[0][0]
'http://www.site2.local'
>>> ar[0][1]
'http://www.site1.local'
>>>