Walter's ipipe patch:

If calling a function in _getattr() raises an AttributeError, return the
default.

Make xattrs() more robust: If calling __xattrs__() raises an exception
fall back to (None,).

Make xrepr() more robust: If calling __repr__() raises an exception fall
back to using repr().

Replace a generator expression with a list comprehension in the
_BrowserLevel constructor so that ipipe stays Python 2.3 compatible.

Fix handling of empty lists in ibrowse: You can not enter empty lists,
and the browser displays an empty screen with the message <empty>.

IPython/Extensions/ipipe.py

@@ -344,7 +344,10 b' def _getattr(obj, name, default=_default):'
     elif isinstance(name, basestring):
         return getattr(obj, name, default)
     elif callable(name):
+        try:
         return name(obj)
+        except AttributeError:
+            return default
     else:
         try:
             return obj[name]
@@ -444,8 +447,14 b' def xrepr(item, mode):'
     except AttributeError:
         pass
     else:
+        try:
         for x in func(mode):
             yield x
+        except (KeyboardInterrupt, SystemExit):
+            raise
+        except Exception:
+            yield (-1, True)
+            yield (style_default, repr(item))
         return
     if item is None:
         yield (-1, True)
@@ -574,7 +583,12 b' def xattrs(item, mode):'
     except AttributeError:
         return (None,)
     else:
+        try:
         return func(mode)
+        except (KeyboardInterrupt, SystemExit):
+            raise
+        except Exception:
+            return (None,)
 
 
 def xiter(item, mode):
@@ -1887,7 +1901,7 b' if curses is not None:'
         def __init__(self, browser, input, iterator, mainsizey, *attrs):
             self.browser = browser
             self.input = input
-            self.header = list(x for x in xrepr(input, "header") if not isinstance(x[0], int))
+            self.header = [x for x in xrepr(input, "header") if not isinstance(x[0], int)]
             # iterator for the input
             self.iterator = iterator
 
@@ -2626,8 +2640,14 b' if curses is not None:'
 
         def cmd_enterdefault(self):
             level = self.levels[-1]
+            try:
+                item = level.items[level.cury].item
+            except IndexError:
+                self.report(CommandError("No object"))
+                curses.beep()
+            else:
             self.report("entering object (default mode)...")
-            self.enter(level.items[level.cury].item, "default")
+                self.enter(item, "default")
 
         def cmd_leave(self):
             self.report("leave")
@@ -2640,8 +2660,14 b' if curses is not None:'
 
         def cmd_enter(self):
             level = self.levels[-1]
+            try:
+                item = level.items[level.cury].item
+            except IndexError:
+                self.report(CommandError("No object"))
+                curses.beep()
+            else:
             self.report("entering object...")
-            self.enter(level.items[level.cury].item, None)
+                self.enter(item, None)
 
         def cmd_enterattr(self):
             level = self.levels[-1]
@@ -2650,7 +2676,13 b' if curses is not None:'
                 curses.beep()
                 self.report(AttributeError(_attrname(attrname)))
                 return
-            attr = _getattr(level.items[level.cury].item, attrname)
+            try:
+                item = level.items[level.cury].item
+            except IndexError:
+                self.report(CommandError("No object"))
+                curses.beep()
+            else:
+                attr = _getattr(item, attrname)
             if attr is _default:
                 self.report(AttributeError(_attrname(attrname)))
             else:
@@ -2659,8 +2691,14 b' if curses is not None:'
 
         def cmd_detail(self):
             level = self.levels[-1]
+            try:
+                item = level.items[level.cury].item
+            except IndexError:
+                self.report(CommandError("No object"))
+                curses.beep()
+            else:
             self.report("entering detail view for object...")
-            self.enter(level.items[level.cury].item, "detail")
+                self.enter(item, "detail")
 
         def cmd_detailattr(self):
             level = self.levels[-1]
@@ -2669,7 +2707,13 b' if curses is not None:'
                 curses.beep()
                 self.report(AttributeError(_attrname(attrname)))
                 return
-            attr = _getattr(level.items[level.cury].item, attrname)
+            try:
+                item = level.items[level.cury].item
+            except IndexError:
+                self.report(CommandError("No object"))
+                curses.beep()
+            else:
+                attr = _getattr(item, attrname)
             if attr is _default:
                 self.report(AttributeError(_attrname(attrname)))
             else:
@@ -2795,6 +2839,11 b' if curses is not None:'
                         posx += self.addstr(posy, posx, 0, self.scrsizex, msg, self.style_objheadernumber)
                     posx += self.addchr(posy, posx, 0, self.scrsizex, " ", self.scrsizex-posx, self.style_objheadernumber)
 
+                if not level.items:
+                    self.addchr(self._headerlines, 0, 0, self.scrsizex, " ", self.scrsizex, self.style_colheader)
+                    self.addstr(self._headerlines+1, 0, 0, self.scrsizex, " <empty>", style_error)
+                    scr.clrtobot()
+                else:
                 # Paint column headers
                 scr.move(self._headerlines, 0)
                 scr.addstr(" %*s " % (level.numbersizex, "#"), self.getstyle(self.style_colheader))