catch NotImplementedError, not NotImplemented

in _ipython_display_

IPython/core/display.py

@@ -115,17 +115,23 b' def display(*objs, **kwargs):'
 
     for obj in objs:
 
-        # If _ipython_display_ is defined, use that to display this object.  If
-        # it returns NotImplemented, use the _repr_ logic (default).
-        if not hasattr(obj, '_ipython_display_') or obj._ipython_display_(**kwargs) is NotImplemented:
-            if raw:
-                publish_display_data('display', obj, metadata)
-            else:            
-                format_dict, md_dict = format(obj, include=include, exclude=exclude)
-                if metadata:
-                    # kwarg-specified metadata gets precedence
-                    _merge(md_dict, metadata)
-                publish_display_data('display', format_dict, md_dict)
+        # If _ipython_display_ is defined, use that to display this object.
+        display_method = getattr(obj, '_ipython_display_', None)
+        if display_method is not None:
+            try:
+                display_method(**kwargs)
+            except NotImplementedError:
+                pass
+            else:
+                continue
+        if raw:
+            publish_display_data('display', obj, metadata)
+        else:
+            format_dict, md_dict = format(obj, include=include, exclude=exclude)
+            if metadata:
+                # kwarg-specified metadata gets precedence
+                _merge(md_dict, metadata)
+            publish_display_data('display', format_dict, md_dict)
 
 
 def display_pretty(*objs, **kwargs):

IPython/core/displayhook.py

@@ -241,16 +241,21 b' class DisplayHook(Configurable):'
         """
         self.check_for_underscore()
         if result is not None and not self.quiet():
-            # If _ipython_display_ is defined, use that to display this object.  If
-            # it returns NotImplemented, use the _repr_ logic (default).
-            if not hasattr(result, '_ipython_display_') or result._ipython_display_() is NotImplemented:
-                self.start_displayhook()
-                self.write_output_prompt()
-                format_dict, md_dict = self.compute_format_data(result)
-                self.write_format_data(format_dict, md_dict)
-                self.update_user_ns(result)
-                self.log_output(format_dict)
-                self.finish_displayhook()
+            # If _ipython_display_ is defined, use that to display this object.
+            display_method = getattr(result, '_ipython_display_', None)
+            if display_method is not None:
+                try:
+                    return display_method()
+                except NotImplementedError:
+                    pass
+            
+            self.start_displayhook()
+            self.write_output_prompt()
+            format_dict, md_dict = self.compute_format_data(result)
+            self.write_format_data(format_dict, md_dict)
+            self.update_user_ns(result)
+            self.log_output(format_dict)
+            self.finish_displayhook()
 
     def flush(self):
         if not self.do_full_cache: