Changed children list to CTuple.

Also removed some unused refences in the widget code
and added support for tuples in the pack/unpack code.

IPython/html/widgets/widget.py

@@ -308,7 +308,7 b' class Widget(LoggingConfigurable):'
         their model ids.  Return value must be JSON-able."""
         if isinstance(x, dict):
             return {k: self._pack_widgets(v) for k, v in x.items()}
-        elif isinstance(x, list):
+        elif isinstance(x, (list, tuple)):
             return [self._pack_widgets(v) for v in x]
         elif isinstance(x, Widget):
             return x.model_id
@@ -322,7 +322,7 b' class Widget(LoggingConfigurable):'
         their model ids."""
         if isinstance(x, dict):
             return {k: self._unpack_widgets(v) for k, v in x.items()}
-        elif isinstance(x, list):
+        elif isinstance(x, (list, tuple)):
             return [self._unpack_widgets(v) for v in x]
         elif isinstance(x, string_types):
             return x if x not in Widget.widgets else Widget.widgets[x]
@@ -412,7 +412,7 b' class DOMWidget(Widget):'
             be added to.
         """
         class_list = class_names
-        if isinstance(class_list, list):
+        if isinstance(class_list, (list, tuple)):
             class_list = ' '.join(class_list)
 
         self.send({
@@ -433,7 +433,7 b' class DOMWidget(Widget):'
             be removed from.
         """
         class_list = class_names
-        if isinstance(class_list, list):
+        if isinstance(class_list, (list, tuple)):
             class_list = ' '.join(class_list)
 
         self.send({

IPython/html/widgets/widget_bool.py

@@ -14,7 +14,7 b' Represents a boolean using a widget.'
 # Imports
 #-----------------------------------------------------------------------------
 from .widget import DOMWidget
-from IPython.utils.traitlets import Unicode, Bool, List
+from IPython.utils.traitlets import Unicode, Bool
 
 #-----------------------------------------------------------------------------
 # Classes

IPython/html/widgets/widget_container.py

@@ -14,7 +14,7 b' Represents a container that can be used to group other widgets.'
 # Imports
 #-----------------------------------------------------------------------------
 from .widget import DOMWidget
-from IPython.utils.traitlets import Unicode, Bool, List, Instance
+from IPython.utils.traitlets import Unicode, CTuple, Instance
 
 #-----------------------------------------------------------------------------
 # Classes
@@ -24,8 +24,8 b' class ContainerWidget(DOMWidget):'
 
     # Keys, all private and managed by helper methods.  Flexible box model
     # classes...
-    children = List(Instance(DOMWidget))
-    _children = List(Instance(DOMWidget), sync=True)
+    children = CTuple(Instance(DOMWidget))
+    _children = CTuple(Instance(DOMWidget), sync=True)
 
     def _children_changed(self, name, old, new):
         """Validate children list.

IPython/html/widgets/widget_float.py

@@ -14,7 +14,7 b' Represents an unbounded float using a widget.'
 # Imports
 #-----------------------------------------------------------------------------
 from .widget import DOMWidget
-from IPython.utils.traitlets import Unicode, CFloat, Bool, List, Enum
+from IPython.utils.traitlets import Unicode, CFloat, Bool, Enum
 
 #-----------------------------------------------------------------------------
 # Classes

IPython/html/widgets/widget_int.py

@@ -14,7 +14,7 b' Represents an unbounded int using a widget.'
 # Imports
 #-----------------------------------------------------------------------------
 from .widget import DOMWidget
-from IPython.utils.traitlets import Unicode, CInt, Bool, List, Enum
+from IPython.utils.traitlets import Unicode, CInt, Bool, Enum
 
 #-----------------------------------------------------------------------------
 # Classes

IPython/html/widgets/widget_selectioncontainer.py

@@ -15,7 +15,7 b' pages.'
 # Imports
 #-----------------------------------------------------------------------------
 from .widget_container import ContainerWidget
-from IPython.utils.traitlets import Unicode, Dict, CInt, List, Instance
+from IPython.utils.traitlets import Unicode, Dict, CInt
 
 #-----------------------------------------------------------------------------
 # Classes

IPython/html/widgets/widget_string.py

@@ -14,7 +14,7 b' Represents a unicode string using a widget.'
 # Imports
 #-----------------------------------------------------------------------------
 from .widget import DOMWidget, CallbackDispatcher
-from IPython.utils.traitlets import Unicode, Bool, List
+from IPython.utils.traitlets import Unicode, Bool
 
 #-----------------------------------------------------------------------------
 # Classes