Use ternary operator for callback registration

IPython/utils/eventful.py

@@ -50,10 +50,7 b' class EventfulDict(dict):'
             The callback should have a signature of callback(key, value).  The
             callback should return a boolean True if the additon should be
             canceled, False or None otherwise."""
-        if callable(callback):
-            self._add_callback = callback
-        else:
-            self._add_callback = _void
+        self._add_callback = callback if callable(callback) else _void
 
     def on_del(self, callback):
         """Register a callback for when an item is deleted from the dict.
@@ -66,11 +63,8 b' class EventfulDict(dict):'
             The callback should have a signature of callback(key).  The
             callback should return a boolean True if the deletion should be
             canceled, False or None otherwise."""
-        if callable(callback):
-            self._del_callback = callback
-        else:
-            self._del_callback = _void
-
+        self._del_callback = callback if callable(callback) else _void
+        
     def on_set(self, callback):
         """Register a callback for when an item is changed in the dict.
 
@@ -82,11 +76,8 b' class EventfulDict(dict):'
             The callback should have a signature of callback(key, value).  The
             callback should return a boolean True if the change should be
             canceled, False or None otherwise."""
-        if callable(callback):
-            self._set_callback = callback
-        else:
-            self._set_callback = _void
-
+        self._set_callback = callback if callable(callback) else _void
+        
     def pop(self, key):
         """Returns the value of an item in the dictionary and then deletes the
         item from the dictionary."""
@@ -182,11 +173,8 b' class EventfulList(list):'
             The callback should have a signature of callback(index, value).  The
             callback should return a boolean True if the insertion should be
             canceled, False or None otherwise."""
-        if callable(callback):
-            self._insert_callback = callback
-        else:
-            self._insert_callback = _void
-
+        self._insert_callback = callback if callable(callback) else _void
+        
     def on_del(self, callback):
         """Register a callback for item deletion.
 
@@ -198,10 +186,7 b' class EventfulList(list):'
             The callback should have a signature of callback(index).  The
             callback should return a boolean True if the deletion should be
             canceled, False or None otherwise."""
-        if callable(callback):
-            self._del_callback = callback
-        else:
-            self._del_callback = _void
+        self._del_callback = callback if callable(callback) else _void
         
     def on_set(self, callback):
         """Register a callback for items are set.
@@ -215,10 +200,7 b' class EventfulList(list):'
             The callback should have a signature of callback(index, value).  The
             callback should return a boolean True if the set should be
             canceled, False or None otherwise."""
-        if callable(callback):
-            self._set_callback = callback
-        else:
-            self._set_callback = _void
+        self._set_callback = callback if callable(callback) else _void
         
     def on_reverse(self, callback):
         """Register a callback for list reversal.
@@ -228,10 +210,7 b' class EventfulList(list):'
             The callback should have a signature of callback().  The
             callback should return a boolean True if the reverse should be
             canceled, False or None otherwise."""
-        if callable(callback):
-            self._reverse_callback = callback
-        else:
-            self._reverse_callback = _void
+        self._reverse_callback = callback if callable(callback) else _void
         
     def on_sort(self, callback):
         """Register a callback for sortting of the list.
@@ -242,10 +221,7 b' class EventfulList(list):'
             method or `callback(*pargs, **kwargs)` as a catch all. The callback 
             should return a boolean True if the reverse should be canceled, 
             False or None otherwise."""
-        if callable(callback):
-            self._sort_callback = callback
-        else:
-            self._sort_callback = _void
+        self._sort_callback = callback if callable(callback) else _void
         
     def append(self, x):
         """Add an item to the end of the list."""