=== modified file 'IPython/extensions/ipy_traits_completer.py'
--- IPython/extensions/ipy_traits_completer.py	2009-07-02 03:36:02 +0000
+++ IPython/extensions/ipy_traits_completer.py	2009-08-19 22:53:09 +0000
@@ -44,13 +44,14 @@
 =====
 
   - This requires Python 2.4 to work (I use sets).  I don't think anyone is
-  using traits with 2.3 anyway, so that's OK.
+    using traits with 2.3 anyway, so that's OK.
+
+  - Imports from enthought.traits are deferred until an object with a class that
+    looks like it subclasses from HasTraits comes along. This test is done by
+    looking at the name of the class and its superclasses.
 """
 
 #############################################################################
-# External imports
-from enthought.traits import api as T
-
 # IPython imports
 from IPython.core.ipapi import TryNext, get as ipget
 from IPython.utils.genutils import dir2
@@ -70,11 +71,37 @@
 
 # Set of names that Traits automatically adds to ANY traits-inheriting object.
 # These are the names we'll filter out.
-TRAIT_NAMES = set( dir2(T.HasTraits()) ) - set( dir2(object()) )
+TRAIT_NAMES = None
+def get_trait_names():
+    global TRAIT_NAMES
+    from enthought.traits.api import HasTraits
+    if TRAIT_NAMES is None:
+        TRAIT_NAMES = set( dir2(HasTraits()) ) - set( dir2(object()) )
+    else:
+        return TRAIT_NAMES
 
 #############################################################################
 # Code begins
 
+def looks_like_isinstance(obj, classname):
+    """ Return True if the object has a class or superclass with the given class
+    name.
+
+    Ignores old-style classes.
+    """
+    from types import InstanceType
+
+    t = type(obj)
+    if t is InstanceType:
+        # Old-style classes.
+        return False
+    elif t.__name__ == classname:
+        return True
+    for klass in t.__mro__:
+        if klass.__name__ == classname:
+            return True
+    return False
+
 def trait_completer(self,event):
     """A custom IPython tab-completer that is traits-aware.
 
@@ -93,7 +120,13 @@
 
     obj = oinfo['obj']
     # OK, we got the object.  See if it's traits, else punt
-    if not isinstance(obj,T.HasTraits):
+    if not looks_like_isinstance(obj, 'HasTraits'):
+        raise TryNext
+
+    # Defer import until here so as not to require Traits until we get something
+    # that looks like it might be a HasTraits instance.
+    from enthought.traits.api import HasTraits
+    if not isinstance(obj, HasTraits):
         raise TryNext
 
     # it's a traits object, don't show the tr* attributes unless the completion
@@ -114,7 +147,7 @@
     #print '\nastart:<%r>' % attr_start  # dbg
 
     if len(attr_start)<COMPLETE_THRESHOLD:
-        attrs = list(set(attrs) - TRAIT_NAMES)
+        attrs = list(set(attrs) - get_trait_names())
         
     # The base of the completion, so we can form the final results list
     bdot = base+'.'
@@ -149,13 +182,14 @@
 #############################################################################
 if __name__ == '__main__':
     # Testing/debugging
+    from enthought.traits.api import HasTraits
 
     # A sorted list of the names we'll filter out
     TNL = list(TRAIT_NAMES)
     TNL.sort()
 
     # Make a few objects for testing
-    class TClean(T.HasTraits): pass
+    class TClean(HasTraits): pass
     class Bunch(object): pass
     # A clean traits object
     t = TClean()