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Author: JelleZijlstra

peps/pep-0661.rst

@@ -146,6 +146,17 @@ A new built-in callable named ``sentinel`` will be added.
     >>> MISSING
     MISSING
 
+``sentinel()`` takes a single positional-only argument, ``name``, which must
+be a ``str``.  Passing a non-string raises ``TypeError``.  The name is used as
+the sentinel's name and repr.
+
+Sentinel objects have two public attributes:
+
+* ``__name__`` is the sentinel's name.
+* ``__module__`` is the name of the module where ``sentinel()`` was called.
+
+``sentinel`` may not be subclassed.
+
 Each call to ``sentinel(name)`` returns a new sentinel object.  If a sentinel
 is needed in more than one place, it should be assigned to a variable and that
 same object should be reused explicitly, just as with the common
@@ -269,10 +280,15 @@ behavior follows::
     class sentinel:
         """Unique sentinel values."""
 
-        __slots__ = ("_name", "_module_name")
+        __slots__ = ("__name__", "_module_name")
+
+        def __init_subclass__(cls):
+            raise TypeError("type 'sentinel' is not an acceptable base type")
 
         def __init__(self, name, /):
-            self._name = str(name)
+            if not isinstance(name, str):
+                raise TypeError("sentinel name must be a string")
+            self.__name__ = name
             self._module_name = sys._getframemodulename(1)
             if self._module_name is None:
                 self._module_name = __name__
@@ -282,10 +298,10 @@ behavior follows::
             return self._module_name
 
         def __repr__(self):
-            return self._name
+            return self.__name__
 
         def __reduce__(self):
-            return self._name
+            return self.__name__
 
         def __copy__(self):
             return self