Issue #16049: add abc.ABC helper class.

Patch by Bruno Dupuis.

2 files changed, 19 insertions, 0 deletions

diff --git a/Lib/abc.py b/Lib/abc.py
index 09778e8..e807895 100644
--- a/Lib/abc.py
+++ b/Lib/abc.py
@@ -226,3 +226,9 @@ class ABCMeta(type):
         # No dice; update negative cache
         cls._abc_negative_cache.add(subclass)
         return False
+
+class ABC(metaclass=ABCMeta):
+    """Helper class that provides a standard way to create an ABC using
+    inheritance.
+    """
+    pass
diff --git a/Lib/test/test_abc.py b/Lib/test/test_abc.py
index 653c957..3498524 100644
--- a/Lib/test/test_abc.py
+++ b/Lib/test/test_abc.py
@@ -96,6 +96,19 @@ class TestLegacyAPI(unittest.TestCase):
 
 class TestABC(unittest.TestCase):
 
+    def test_ABC_helper(self):
+        # create an ABC using the helper class and perform basic checks
+        class C(abc.ABC):
+            @classmethod
+            @abc.abstractmethod
+            def foo(cls): return cls.__name__
+        self.assertEqual(type(C), abc.ABCMeta)
+        self.assertRaises(TypeError, C)
+        class D(C):
+            @classmethod
+            def foo(cls): return super().foo()
+        self.assertEqual(D.foo(), 'D')
+
     def test_abstractmethod_basics(self):
         @abc.abstractmethod
         def foo(self): pass