Recupérer code htlm pyhton 3

Bonjour,

je souhaite faire un programme simple afin de récuperer le code HTML d'une page web .
voici mon code :

stock=urllib.request.urlopen("site")
print(stock.read())

Ce pendant lorsque j’exécute ce dernier je reçois une error 403 HTTP

"File "/Users/utilisateur/PycharmProjects/adidasscan/adidasscan.py", line 9, in <module>
stock=urllib.request.urlopen("site")
File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/urllib/request.py", line 156, in urlopen
return opener.open(url, data, timeout)
File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/urllib/request.py", line 475, in open
response = meth(req, response)
File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/urllib/request.py", line 587, in http_response
'http', request, response, code, msg, hdrs)
File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/urllib/request.py", line 513, in error
return self._call_chain(*args)
File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/urllib/request.py", line 447, in _call_chain
result = func(*args)
File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/urllib/request.py", line 595, in http_error_default
raise HTTPError(req.full_url, code, msg, hdrs, fp)
urllib.error.HTTPError: HTTP Error 403: Forbidden "


Que faire ? merci de votre aide