Issue #26778: Fixed "a/an/and" typos in code comment and documentation.
diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index a467ddd..313fadf 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -439,7 +439,7 @@
         return self.__closed
 
     def _checkClosed(self, msg=None):
-        """Internal: raise an ValueError if file is closed
+        """Internal: raise a ValueError if file is closed
         """
         if self.closed:
             raise ValueError("I/O operation on closed file."