Differences between revisions 4 and 7 (spanning 3 versions)

Writing Exception Classes

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:

   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 4 as of 2003-09-06 19:51:18 → 
  Size: 1196
  Editor: dsl254-010-130
  Comment: Exceptions derive from exception. Need call parent initializer?
+   ← Revision 7 as of 2003-09-07 15:24:11 → ⇥
  Size: 1014
  Editor: dsl254-010-130
  Comment:
-Deletions are marked like this.
+Additions are marked like this.
 Line 3:
-I (LionKimbro) don't know much about writing exception classes; Here's hoping someone rewrites this better.

Derive Exception classes from Exception:
+Exception classes are not special, you just derive them from Exception:
-Line 12:
+Line 10:
+        Exception.__init__(self, 'Host Not Found exception: missing %s' % host)
-Line 13:
+Line 12:
-  ''Do we call {{{Exception.__init__( self )}}}..?'' -- LionKimbro [[DateTime(2003-09-06T19:51:18Z)]]
-Line 23:
+Line 20:
-    print "Host Not Found:", X.host
+    # Handle exception.
    # "X" is the HostNotFound instance.
-Line 26:
+Line 24:
-== Overloading __str__ ==
+== See Also ==
-Line 28:
+Line 26:
-You can overload {{{__str__}}} to get the exception to explain itself:

{{{
#!python
class HostNotFound(Exception):
    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 53:
+Line 30:
-  * 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)]]

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Writing Exception Classes

See Also

Questions