add further note about what's passed to optionxform

diff --git a/Doc/library/configparser.rst b/Doc/library/configparser.rst
index 1af14cccc091515e05a0f78f0cbfbfe74b90b8ea..2d8aa50e4c290de5ba1e8c58710ebf03e618d79b 100644 (file)
--- a/Doc/library/configparser.rst
+++ b/Doc/library/configparser.rst
@@ -349,6 +349,9 @@ RawConfigParser Objects
       ...
       cfgparser.optionxform = str
 
+   Note that when reading configuration files, whitespace around the
+   option names are stripped before :meth:``optionxform`` is called.
+
 
 .. _configparser-objects: