Add new %debug magic, activates the interactive debugger immediately on the

last traceback without having to rerun any code.

IPython/Magic.py

@@ -1,7 +1,7 b''
 # -*- coding: utf-8 -*-
 """Magic functions for InteractiveShell.
 
-$Id: Magic.py 1941 2006-11-26 22:24:43Z vivainio $"""
+$Id: Magic.py 1956 2006-11-30 05:22:31Z fperez $"""
 
 #*****************************************************************************
 #       Copyright (C) 2001 Janko Hauser <[e-mail]> and
@@ -1164,14 +1164,21 b' Currently the magic system has the following functions:\\n"""'
         self.shell.logger.logstate()
         
     def magic_pdb(self, parameter_s=''):
-        """Control the calling of the pdb interactive debugger.
+        """Control the automatic calling of the pdb interactive debugger.
 
         Call as '%pdb on', '%pdb 1', '%pdb off' or '%pdb 0'. If called without
         argument it works as a toggle.
 
         When an exception is triggered, IPython can optionally call the
         interactive pdb debugger after the traceback printout. %pdb toggles
-        this feature on and off."""
+        this feature on and off.
+
+        The initial state of this feature is set in your ipythonrc
+        configuration file (the variable is called 'pdb').
+
+        If you want to just activate the debugger AFTER an exception has fired,
+        without having to type '%pdb on' and rerunning your code, you can use
+        the %debug magic."""
 
         par = parameter_s.strip().lower()
 
@@ -1184,12 +1191,27 b' Currently the magic system has the following functions:\\n"""'
                 return
         else:
             # toggle
-            new_pdb = not self.shell.InteractiveTB.call_pdb
+            new_pdb = not self.shell.call_pdb
 
         # set on the shell
         self.shell.call_pdb = new_pdb
         print 'Automatic pdb calling has been turned',on_off(new_pdb)
 
+    def magic_debug(self, parameter_s=''):
+        """Activate the interactive debugger in post-mortem mode.
+
+        If an exception has just occurred, this lets you inspect its stack
+        frames interactively.  Note that this will always work only on the last
+        traceback that occurred, so you must call this quickly after an
+        exception that you wish to inspect has fired, because if another one
+        occurs, it clobbers the previous one.
+
+        If you want IPython to automatically do this on every exception, see
+        the %pdb magic for more details.
+        """
+        
+        self.shell.debugger(force=True)
+
     def magic_prun(self, parameter_s ='',user_mode=1,
                    opts=None,arg_lst=None,prog_ns=None):
 

IPython/iplib.py

@@ -6,7 +6,7 b' Requires Python 2.3 or newer.'
 
 This file contains all the classes and helper functions specific to IPython.
 
-$Id: iplib.py 1935 2006-11-26 20:42:29Z vivainio $
+$Id: iplib.py 1956 2006-11-30 05:22:31Z fperez $
 """
 
 #*****************************************************************************
@@ -1412,20 +1412,31 b' want to merge them back into the new files.""" % locals()'
                     value = msg, (filename, lineno, offset, line)
         self.SyntaxTB(etype,value,[])
 
-    def debugger(self):
-        """Call the pydb/pdb debugger."""
+    def debugger(self,force=False):
+        """Call the pydb/pdb debugger.
 
-        if not self.rc.pdb:
+        Keywords:
+
+          - force(False): by default, this routine checks the instance call_pdb
+          flag and does not actually invoke the debugger if the flag is false.
+          The 'force' option forces the debugger to activate even if the flag
+          is false.
+        """
+
+        if not (force or self.call_pdb):
             return
+
         have_pydb = False
         if sys.version[:3] >= '2.5':
+            # use pydb if available
             try:
                 from pydb import pm
                 have_pydb = True
             except ImportError:
                 pass
         if not have_pydb:
-            from pdb import pm
+            # fallback to our internal debugger
+            pm = lambda : self.InteractiveTB.debugger(force=True)
         self.history_saving_wrapper(pm)()
 
     def showtraceback(self,exc_tuple = None,filename=None,tb_offset=None):

IPython/ultraTB.py

@@ -60,7 +60,7 b' You can implement other color schemes easily, the syntax is fairly'
 self-explanatory. Please send back new schemes you develop to the author for
 possible inclusion in future releases.
 
-$Id: ultraTB.py 1787 2006-09-27 06:56:29Z fperez $"""
+$Id: ultraTB.py 1956 2006-11-30 05:22:31Z fperez $"""
 
 #*****************************************************************************
 #       Copyright (C) 2001 Nathaniel Gray <[e-mail]>
@@ -666,8 +666,16 b' class VerboseTB(TBTools):'
         # return all our info assembled as a single string
         return '%s\n\n%s\n%s' % (head,'\n'.join(frames),''.join(exception[0]) )
 
-    def debugger(self):
-        """Call up the pdb debugger if desired, always clean up the tb reference.
+    def debugger(self,force=False):
+        """Call up the pdb debugger if desired, always clean up the tb
+        reference.
+
+        Keywords:
+
+          - force(False): by default, this routine checks the instance call_pdb
+          flag and does not actually invoke the debugger if the flag is false.
+          The 'force' option forces the debugger to activate even if the flag
+          is false.
 
         If the call_pdb flag is set, the pdb interactive debugger is
         invoked. In all cases, the self.tb reference to the current traceback
@@ -678,7 +686,7 b' class VerboseTB(TBTools):'
         requires a special setup for the readline completers, you'll have to
         fix that by hand after invoking the exception handler."""
 
-        if self.call_pdb:
+        if force or self.call_pdb:
             if self.pdb is None:
                 self.pdb = Debugger.Pdb(
                     self.color_scheme_table.active_scheme_name)
@@ -688,7 +696,10 b' class VerboseTB(TBTools):'
             sys.displayhook = sys.__displayhook__
             self.pdb.reset()
             # Find the right frame so we don't pop up inside ipython itself
-            etb = self.tb
+            if hasattr(self,'tb'):
+                etb = self.tb
+            else:
+                etb = self.tb = sys.last_traceback
             while self.tb.tb_next is not None:
                 self.tb = self.tb.tb_next
             try:
@@ -696,12 +707,11 b' class VerboseTB(TBTools):'
                     etb = etb.tb_next
                 self.pdb.botframe = etb.tb_frame
                 self.pdb.interaction(self.tb.tb_frame, self.tb)
-            except:
-                print '*** ERROR ***'
-                print 'This version of pdb has a bug and crashed.'
-                print 'Returning to IPython...'
-            sys.displayhook = dhook
-        del self.tb
+            finally:
+                sys.displayhook = dhook
+            
+        if hasattr(self,'tb'):
+            del self.tb
 
     def handler(self, info=None):
         (etype, evalue, etb) = info or sys.exc_info()

doc/ChangeLog

@@ -1,4 +1,11 b''
-2006-11-2(8  Ville Vainio  <[e-mail]>
[phone]  Fernando Perez  <[e-mail]>
+
+	* IPython/Magic.py (magic_debug): new %debug magic to activate the
+	interactive debugger on the last traceback, without having to call
+	%pdb and rerun your code.  Made minor changes in various modules,
+	should automatically recognize pydb if available.
+
[phone]  Ville Vainio  <[e-mail]>
 
 	* completer.py: If the text start with !, show file completions
 	properly. This helps when trying to complete command name