gh-151443: Fix documented default of `unittest.mock.mock_open`'s `read_data` paramet...

diff --git a/Doc/library/unittest.mock.rst b/Doc/library/unittest.mock.rst
index 6ba1b87ea942a9014d219f9daeb79cce5b4ee6d8..5e28a8ada595ef164b46583502cce35cd1035e6b 100644 (file)
--- a/Doc/library/unittest.mock.rst
+++ b/Doc/library/unittest.mock.rst
@@ -2539,7 +2539,7 @@ Alternatively you can just use ``vars(my_mock)`` (instance members) and
 mock_open
 ~~~~~~~~~
 
-.. function:: mock_open(mock=None, read_data=None)
+.. function:: mock_open(mock=None, read_data='')
 
    A helper function to create a mock to replace the use of :func:`open`. It works
    for :func:`open` called directly or used as a context manager.