Merge pull request #29 from vidartf/fix-sentinel

Copy Sentinel implementation from traitlets

Author: SylvainCorlay

traittypes/traittypes.py

@@ -1,7 +1,8 @@
 import inspect
 import warnings
 
-from traitlets import TraitType, TraitError, Undefined, Sentinel
+from traitlets import TraitType, TraitError, Undefined
+from .utils import Sentinel
 
 class _DelayedImportError(object):
     def __init__(self, package_name):

traittypes/utils.py

@@ -0,0 +1,22 @@
+"""Sentinel class for constants with useful reprs"""
+
+# Copyright (c) Jupyter Development Team.
+# Distributed under the terms of the Modified BSD License.
+
+
+class Sentinel(object):
+
+    def __init__(self, name, module, docstring=None):
+        self.name = name
+        self.module = module
+        if docstring:
+            self.__doc__ = docstring
+
+    def __repr__(self):
+        return str(self.module) + '.' + self.name
+
+    def __copy__(self):
+        return self
+
+    def __deepcopy__(self, memo):
+        return self