Index: Doc/library/contextlib.rst
===================================================================
--- Doc/library/contextlib.rst	(revision 85340)
+++ Doc/library/contextlib.rst	(working copy)
@@ -85,6 +85,27 @@
    ``page.close()`` will be called when the :keyword:`with` block is exited.
 
 
+.. function:: nullcontext()
+
+   Return a context manager that executes block without doing any
+   additional processing.
+
+   Such a context manager can be Used as a standin if a particular
+   block of code is only sometimes used with a normal context
+   manager::
+
+      with optional_cm or nullcontext():
+          # Perform operation, using the specified CM if one is given
+
+   ``nullcontext`` is basically equivalent to::
+
+      from contextlib import contextmanager
+
+      @contextmanager
+      def nullcontext():
+          yield
+
+
 .. class:: ContextDecorator()
 
    A base class that enables a context manager to also be used as a decorator.
Index: Lib/contextlib.py
===================================================================
--- Lib/contextlib.py	(revision 85340)
+++ Lib/contextlib.py	(working copy)
@@ -4,7 +4,7 @@
 from functools import wraps
 from warnings import warn
 
-__all__ = ["contextmanager", "closing", "ContextDecorator"]
+__all__ = ["contextmanager", "closing", "ContextDecorator", "nullcontext"]
 
 
 class ContextDecorator(object):
@@ -119,3 +119,25 @@
         return self.thing
     def __exit__(self, *exc_info):
         self.thing.close()
+
+
+class NullContext:
+    """Helper for nullcontext."""
+    def __enter__(self):
+        pass
+    def __exit__(self, *exc_info):
+        pass
+
+_nullcontext = NullContext()
+
+def nullcontext():
+    """
+    No-op context manager, executes block without doing any additional processing.
+
+    Used as a standin if a particular block of code is only sometimes
+    used with a normal context manager:
+
+      with optional_cm or nullcontext():
+          # Perform operation, using the specified CM if one is given
+    """
+    return _nullcontext
Index: Lib/test/test_contextlib.py
===================================================================
--- Lib/test/test_contextlib.py	(revision 85340)
+++ Lib/test/test_contextlib.py	(working copy)
@@ -365,6 +365,15 @@
         self.assertEqual(state, [1, 'something', 999])
 
 
+class NullTestCase(unittest.TestCase):
+
+    def test_null(self):
+        state = []
+        with nullcontext():
+            state.append(1)
+        self.assertEqual(state, [1])
+
+
 # This is needed to make the test actually run under regrtest.py!
 def test_main():
     support.run_unittest(__name__)