Differences between revisions 1 and 6 (spanning 5 versions)

Writing Exception Classes

I (LionKimbro) don't know much about writing exception classes; Here's hoping someone rewrites this better.

Exception classes are not special, you just derive them from Exception:

   1 class HostNotFound(Exception):
   2     def __init__( self, host ):
   3         self.host = host
   4         Exception.__init__(self, 'Host Not Found exception: missing %s' % host)

You may later write:

Toggle line numbers

   1 try:
   2     raise HostNotFound( "taoriver.net" )
   3 except HostNotFound, X:
   4     # Handle exception.
   5     # "X" is the HostNotFound instance.

Questions

How do you relay the traceback information? Relay the traceback information? Moving it higher up the call-stack? Could you try to explain your question?
- When you're logging exceptions, you want access to the traceback information to. After some research, I believe what you use is extract_tb or extract_stack from the traceback module. -- 216.254.10.130 DateTime(2003-09-07T15:23:43Z)
What better exception-foo is out there?

-  ⇤ ← Revision 1 as of 2003-09-06 18:34:16 → 
  Size: 1097
  Editor: dsl254-010-130
  Comment: Initial version, Req for Comment.
+   ← Revision 6 as of 2003-09-07 15:23:43 → ⇥
  Size: 1125
  Editor: dsl254-010-130
  Comment: __str__ section no longer necessary, answered question, added "See Also".
-Deletions are marked like this.
+Additions are marked like this.
 Line 5:
-Exception classes are not special; You just write an ordinary class:
+Exception classes are not special, you just derive them from Exception:
 Line 9:
-class HostNotFound:
+class HostNotFound(Exception):
 Line 12:
+        Exception.__init__(self, 'Host Not Found exception: missing %s' % host)
-Line 21:
+Line 22:
-    print "Host Not Found:", X.host
+    # Handle exception.
    # "X" is the HostNotFound instance.
-Line 24:
+Line 26:
-== Overloading __str__ ==
+== See Also ==
-Line 26:
+Line 28:
-You can overload {{{__str__}}} to get the exception to explain itself:

{{{
#!python
class HostNotFound:
    def __init__( self, host ):
        self.host = host
    def __str__( self ):
        return "Host Not Found exception: missing %s" % self.host
}}}

That way, you only need print the exception instance:

{{{
#!python
try:
    raise HostNotFound( "taoriver.net" )
except HostNotFound, X:
    print X
}}}

I don't know if this is a good idea or not.
+HandlingExceptions, TracebackModule
-Line 51:
+Line 32:
-  * How do you relay the traceback information?
+  * How do you relay the traceback information? ''Relay the traceback information? Moving it higher up the call-stack? Could you try to explain your question?''
     * When you're logging exceptions, you want access to the traceback information to. After some research, I believe what you use is extract_tb or extract_stack from the traceback module. -- 216.254.10.130 [[DateTime(2003-09-07T15:23:43Z)]]

Page

User

Writing Exception Classes

See Also

Questions