From 23306a412d316235e797c767522336e41d1cfd74 2012-08-16 22:18:24
From: MinRK <benjaminrk@gmail.com>
Date: 2012-08-16 22:18:24
Subject: [PATCH] always perform requested trait assignments

Some assignments do not change *value*, but do change the object,
and these should not be ignored.

For instance, container objects are currently impossible to assign
if they evaluate as equal.

---

diff --git a/IPython/utils/traitlets.py b/IPython/utils/traitlets.py
index eae3f0d..0915520 100644
--- a/IPython/utils/traitlets.py
+++ b/IPython/utils/traitlets.py
@@ -302,8 +302,8 @@ class TraitType(object):
     def __set__(self, obj, value):
         new_value = self._validate(obj, value)
         old_value = self.__get__(obj)
+        obj._trait_values[self.name] = new_value
         if old_value != new_value:
-            obj._trait_values[self.name] = new_value
             obj._notify_trait(self.name, old_value, new_value)
 
     def _validate(self, obj, value):