python · isidentical · Jul 18, 2021 · Nov 14, 2020
diff --git a/Doc/library/symtable.rst b/Doc/library/symtable.rst
@@ -192,5 +192,5 @@ Examining Symbol Tables

   .. method:: get_namespace()

-      Return the namespace bound to this name.  If more than one namespace is
-      bound, :exc:`ValueError` is raised.
+      Return the namespace bound to this name. If more than one or no namespace
+      is bound to this name, a :exc:`ValueError` is raised.
diff --git a/Lib/symtable.py b/Lib/symtable.py
@@ -306,11 +306,15 @@ def get_namespaces(self):
    def get_namespace(self):
        """Return the single namespace bound to this name.

-        Raises ValueError if the name is bound to multiple namespaces.
+        Raises ValueError if the name is bound to multiple namespaces
+        or no namespace.
        """
-        if len(self.__namespaces) != 1:
+        if len(self.__namespaces) == 0:
+            raise ValueError("name is not bound to any namespaces")
+        elif len(self.__namespaces) > 1:
            raise ValueError("name is bound to multiple namespaces")
-        return self.__namespaces[0]
+        else:
+            return self.__namespaces[0]

 if __name__ == "__main__":
    import os, sys

diff --git a/Lib/test/test_symtable.py b/Lib/test/test_symtable.py
@@ -159,6 +159,10 @@ def test_namespaces(self):
        self.assertEqual(len(ns_test.get_namespaces()), 2)
        self.assertRaises(ValueError, ns_test.get_namespace)

+        ns_test_2 = self.top.lookup("glob")
+        self.assertEqual(len(ns_test_2.get_namespaces()), 0)
+        self.assertRaises(ValueError, ns_test_2.get_namespace)
+
    def test_assigned(self):
        self.assertTrue(self.spam.lookup("x").is_assigned())
        self.assertTrue(self.spam.lookup("bar").is_assigned())