How to catch 'error' type exceptions

[Anand Pillai]

Hi

I am quite familiar with normal python errors which can
be caught by using the try... except... finally clause. But
very often I find other kinds of exceptions raised in my programs.

Here is an example.

<TRACEBACK>
Traceback (most recent call last):
File "D:\Python22\li b\threading.py" , line 414, in __bootstrap
self.run()
File "WebUrlTracker. py", line 213, in run
self.action()
File "WebUrlTracker. py", line 207, in action
self.downloadUr l()
File "WebUrlTracker. py", line 249, in downloadUrl
self.fetchUrl()
File "WebUrlTracker. py", line 319, in fetchUrl
data=self._conn ection.fetchDat a(fetchurl)
File "WebUrlConnecto r.py", line 267, in fetchData
connection.requ est("GET", relpath)
File "D:\Python22\li b\httplib.py", line 702, in request
self._send_requ est(method, url, body, headers)
File "D:\Python22\li b\httplib.py", line 724, in _send_request
self.endheaders ()
File "D:\Python22\li b\httplib.py", line 696, in endheaders
self._send_outp ut()
File "D:\Python22\li b\httplib.py", line 582, in _send_output
self.send(msg)
File "D:\Python22\li b\httplib.py", line 549, in send
self.connect()
File "D:\Python22\li b\httplib.py", line 789, in connect
error: (10060, 'Operation timed out')
</TRACEBACK>

If I try to catch this using the try... except clause it does not work
(actually it raises another error for trying to catch 'error'), i.e the
following code fails.

try:
<Exception generating code>
except error, e:
print e

Could anyone tell me more about these errors and how to deal with
them ? Probably it is already documented in the python reference, but
I have missed it in that case.

Thanks

Anand Pillai

[Alan Kennedy]

Anand Pillai wrote:

<TRACEBACK>
[ Traceback elided ]
File "D:\Python22\li b\httplib.py", line 789, in connect
error: (10060, 'Operation timed out')
</TRACEBACK>

If I try to catch this using the try... except clause it does not work
(actually it raises another error for trying to catch 'error'), i.e the
following code fails.

try:
<Exception generating code>
except error, e:
print e

import socket

try:
<Exception generating code>
except socket.error, e:
print e

HTH,

--
alan kennedy
-----------------------------------------------------
check http headers here: http://xhaus.com/headers
email alan: http://xhaus.com/mailto/alan

[Kevin Cazabon]

Your problem is that "error" is not a valid exception type in Python.
You "should" be trying to catch a specific problem so that you can
handle it appropriately (such as socket.error as mentioned by another
poster).

The lazy, dangerous way would be:

try:
# some error-generating code
except Exception, reason:
print reason

but that's not recommended good coding practice.

Kevin.

py*******@Hotpo p.com (Anand Pillai) wrote in message
news:<84******* *************** ****@posting.go ogle.com>...

Hi

I am quite familiar with normal python errors which can
be caught by using the try... except... finally clause. But
very often I find other kinds of exceptions raised in my programs.

Here is an example.

<TRACEBACK>
Traceback (most recent call last):
File "D:\Python22\li b\threading.py" , line 414, in __bootstrap
self.run()
File "WebUrlTracker. py", line 213, in run
self.action()
File "WebUrlTracker. py", line 207, in action
self.downloadUr l()
File "WebUrlTracker. py", line 249, in downloadUrl
self.fetchUrl()
File "WebUrlTracker. py", line 319, in fetchUrl
data=self._conn ection.fetchDat a(fetchurl)
File "WebUrlConnecto r.py", line 267, in fetchData
connection.requ est("GET", relpath)
File "D:\Python22\li b\httplib.py", line 702, in request
self._send_requ est(method, url, body, headers)
File "D:\Python22\li b\httplib.py", line 724, in _send_request
self.endheaders ()
File "D:\Python22\li b\httplib.py", line 696, in endheaders
self._send_outp ut()
File "D:\Python22\li b\httplib.py", line 582, in _send_output
self.send(msg)
File "D:\Python22\li b\httplib.py", line 549, in send
self.connect()
File "D:\Python22\li b\httplib.py", line 789, in connect
error: (10060, 'Operation timed out')
</TRACEBACK>

If I try to catch this using the try... except clause it does not work
(actually it raises another error for trying to catch 'error'), i.e the
following code fails.

try:
<Exception generating code>
except error, e:
print e

Could anyone tell me more about these errors and how to deal with
them ? Probably it is already documented in the python reference, but
I have missed it in that case.

Thanks

Anand Pillai

[Bengt Richter]

On Mon, 30 Jun 2003 14:21:58 +0100, Alan Kennedy <al****@hotmail .com> wrote:

Anand Pillai wrote:

<TRACEBACK>

[ Traceback elided ]

File "D:\Python22\li b\httplib.py", line 789, in connect
error: (10060, 'Operation timed out')
</TRACEBACK>

If I try to catch this using the try... except clause it does not work
(actually it raises another error for trying to catch 'error'), i.e the
following code fails.

try:
<Exception generating code>
except error, e:
print e

import socket

try:
<Exception generating code>
except socket.error, e:
print e

HTH,

Sometimes a catchall is desirable, e.g. (untested):

try:
<Exception generating code>
except Exception, e:
print '%s: %s' % (e.__class__.__ name__, e)
if isinstance(e, SystemExit): raise # take the exit
except:
print 'Nonstandard Exception %r: %r' % __import__('sys ').exc_info()[:2]

HTH2 ;-)

Regards,
Bengt Richter

[Bengt Richter]

On 30 Jun 2003 13:22:32 -0700, ke***@cazabon.c om (Kevin Cazabon) wrote:

Your problem is that "error" is not a valid exception type in Python.
You "should" be trying to catch a specific problem so that you can
handle it appropriately (such as socket.error as mentioned by another
poster).

The lazy, dangerous way would be:

try:
# some error-generating code
except Exception, reason:
print reason

but that's not recommended good coding practice.

Yes, certainly not internally, unless re-raising all or selected exceptions,
but as an outside wrapper to a whole app, why not? (You could make traceback
printing depend on __debug__ or some other option if desired).

You could also detect and eliminate redundant repetition in a traceback print
of a recursion limit exception. (I think that would be a nice default, BTW).

Regards,
Bengt Richter