I've written a CGI proxy that remotely fetches web pages. I use the
urlopen function in CLientCookie which replaces (and ultimately uses)
the urlopen function in urllib2. What I'd like to do is give a more
useful message to the user when the page fetch fails.
My understanding was that a URLError exception had a 'code' attribute
which was the error code.
I trap the error with a simple : (excuse the horrible indentation,
this is from the middle of a program)
try:
req = urllib2.Request (theurl, txdata, txheaders)
if data['name'] and data['pass']:
import base64
base64string = base64.encodest ring('%s:%s' %
(data['name'], data['pass']))[:-1]
req.add_header( "Authorization" , "Basic %s" %
base64string)
u = openfun(req)
......
except IOError, e: # an error in fetching
the page will raise a URLError which is a subclass of IOError
if not cdone:
print "Content-type: text/html" # this is the
header to the server
print # so is this
blank line
if not hasattr(e, 'code'): # If it's not
an http error - raise it as an error
raise
elif e.code == 401: #
authorisation
print authmess % (theurl, data['mod'])
print authend
elif e.code in errorlist: # standard
http errors
the_err = errorlist[e.code]
print err_mes % (the_err[0], the_err[0], the_err[1])
else: # any others
raise
openfun is urlopen function from ClientCookie (if available) or from
urllib2.
What ought to happen in my limied understanding, is that the exception
(e) should have the attribute 'code' if it a URLError - and that value
ought to tell me what type of error it is... (the error message is
then ina dictionary called errorlist which I nicked from
BaseHTTPServer) .
*However*, when I use it to try to fetch a non-existent page
(expecting a 404 error) - it falls at the first raise statement.
Evidently the exception *is* an IOError, but doesn't have the code
attribute.
*However* - you see the explicit test for a 401 (authentication )
error. I have code that can handle authentication. .. if I go to a page
that requires authentication it picks it up fine...... (so the
URLError in that case does have the code attribute).
The exact error traceback is below - and you can see where urllib2
raises the URLError - because of what it sees as a socket problem...
but it obviously isn't returning the error code properly. Any
suggestions ?
URLError Python 2.2.2: /usr/bin/python
Fri Jul 23 11:06:39 2004
A problem occurred in a Python script. Here is the sequence of
function calls leading up to the error, in the order they occurred.
/home/buildin/public_html/cgi-bin/approx.py
280 print "Content-type: text/html" # this
is the header to the server
281 print # so is
this blank line
282 if not hasattr(e, 'code'): # If
it's not an http error - raise it as an error
283 raise
284
hasattr undefined, e = <urllib2.URLErr or instance>
/home/buildin/public_html/cgi-bin/ClientCookie/_urllib2_suppor t.py in
urlopen(url=<ur llib2.Request instance>, data=None)
969 finally:
970 urlopen_lock.re lease()
971 return _opener.open(ur l, data)
972
973 def urlretrieve(url , filename=None, reporthook=None ,
data=None):
global _opener = <ClientCookie._ urllib2_support .OpenerDirector
instance>, _opener.open = <bound method OpenerDirector. open of
<ClientCookie._ urllib2_support .OpenerDirector instance>>, url =
<urllib2.Reques t instance>, data = None
/home/buildin/public_html/cgi-bin/ClientCookie/_urllib2_suppor t.py in
open(self=<Clie ntCookie._urlli b2_support.Open erDirector instance>,
fullurl=<urllib 2.Request instance>, data=None)
567 req = meth(req)
568
569 response = urllib2.OpenerD irector.open(se lf, req,
data)
570
571 # post-process response
response undefined, global urllib2 = <module 'urllib2' from
'/usr/lib/python2.2/urllib2.pyc'>, urllib2.OpenerD irector = <class
urllib2.OpenerD irector>, urllib2.OpenerD irector.open = <unbound method
OpenerDirector. open>, self =
<ClientCookie._ urllib2_support .OpenerDirector instance>, req =
<ClientCookie._ urllib2_support .Request instance>, data = None
/usr/lib/python2.2/urllib2.py in
open(self=<Clie ntCookie._urlli b2_support.Open erDirector instance>,
fullurl=<Client Cookie._urllib2 _support.Reques t instance>, data=None)
320 type_ = req.get_type()
321 result = self._call_chai n(self.handle_o pen, type_, type_
+ \
322 '_open', req)
323 if result:
324 return result
req = <ClientCookie._ urllib2_support .Request instance>
/usr/lib/python2.2/urllib2.py in
_call_chain(sel f=<ClientCookie ._urllib2_suppo rt.OpenerDirect or
instance>, chain={'file': [<urllib2.FileHa ndler instance>], 'ftp':
[<urllib2.FTPHan dler instance>], 'http':
[<ClientCookie._ urllib2_support .HTTPHandler instance>], 'https':
[<ClientCookie._ urllib2_support .HTTPSHandler instance>], 'unknown':
[<urllib2.Unknow nHandler instance>]}, kind='http',
meth_name='http _open', *args=(<ClientC ookie._urllib2_ support.Request
instance>,))
299 func = getattr(handler , meth_name)
300
301 result = func(*args)
302 if result is not None:
303 return result
result undefined, func = <bound method HTTPHandler.htt p_open of
<ClientCookie._ urllib2_support .HTTPHandler instance>>, args =
(<ClientCookie. _urllib2_suppor t.Request instance>,)
/home/buildin/public_html/cgi-bin/ClientCookie/_urllib2_suppor t.py in
http_open(self= <ClientCookie._ urllib2_support .HTTPHandler instance>,
req=<ClientCook ie._urllib2_sup port.Request instance>)
883 class HTTPHandler(Abs tractHTTPHandle r):
884 def http_open(self, req):
885 return self.do_open(ht tplib.HTTP, req)
886
887 http_request = AbstractHTTPHan dler.do_request _
self = <ClientCookie._ urllib2_support .HTTPHandler instance>,
self.do_open = <bound method HTTPHandler.do_ open of
<ClientCookie._ urllib2_support .HTTPHandler instance>>, global httplib
= <module 'httplib' from '/usr/lib/python2.2/httplib.pyc'>,
httplib.HTTP = <class httplib.HTTP>, req =
<ClientCookie._ urllib2_support .Request instance>
/home/buildin/public_html/cgi-bin/ClientCookie/_urllib2_suppor t.py in
do_open(self=<C lientCookie._ur llib2_support.H TTPHandler instance>,
http_class=<cla ss httplib.HTTP>,
req=<ClientCook ie._urllib2_sup port.Request instance>)
728 h.endheaders()
729 except socket.error, err:
730 raise URLError(err)
731 if req.has_data():
732 h.send(req.get_ data())
global URLError = <class urllib2.URLErro r>, err = <socket.gaierro r
instance>
URLError:
__doc__ = None
__getitem__ = <bound method URLError.__geti tem__ of
<urllib2.URLErr or instance>>
__init__ = <bound method URLError.__init __ of <urllib2.URLErr or
instance>>
__module__ = 'urllib2'
__str__ = <bound method URLError.__str_ _ of <urllib2.URLErr or
instance>>
reason = <socket.gaierro r instance>
Regards,
Fuzzy
http://www.voidspace.org.uk/atlantib...thonutils.html
