Document absoluteness of sys.executable
Closes #13402.
diff --git a/Doc/library/sys.rst b/Doc/library/sys.rst
index 18f916b..d611acf 100644
--- a/Doc/library/sys.rst
+++ b/Doc/library/sys.rst
@@ -202,8 +202,10 @@
.. data:: executable
- A string giving the name of the executable binary for the Python interpreter, on
- systems where this makes sense.
+ A string giving the absolute path of the executable binary for the Python
+ interpreter, on systems where this makes sense. If Python is unable to retrieve
+ the real path to its executable, :data:`sys.executable` will be an empty string
+ or ``None``.
.. function:: exit([arg])