gh-128017: Make a note that sys variables are read-only (#128887)

diff --git a/Doc/library/sys.rst b/Doc/library/sys.rst
index dd6293c722e7ad8d4cc1cb559f7d4addf522e5a2..151fd60532048af0d9402b695e836ab6214d9831 100644 (file)
--- a/Doc/library/sys.rst
+++ b/Doc/library/sys.rst
@@ -8,7 +8,7 @@
 
 This module provides access to some variables used or maintained by the
 interpreter and to functions that interact strongly with the interpreter. It is
-always available.
+always available. Unless explicitly noted otherwise, all variables are read-only.
 
 
 .. data:: abiflags