bpo-35838: document optionxform must be idempotent (GH-12656)

04694a30 · Inada Naoki · GitHub · e6a0e804 · 04694a30
Commit 04694a30 authored Apr 02, 2019 by Inada Naoki Committed by GitHub Apr 02, 2019
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Doc/library/configparser.rst Doc/library/configparser.rst +6 -0

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--- a/Doc/library/configparser.rst
+++ b/Doc/library/configparser.rst
@@ -721,6 +721,12 @@ be overridden by subclasses or by attribute assignment.
     >>> list(custom['Section2'].keys())
     ['AnotherKey']

+  .. note::
+     The optionxform function transforms option names to a canonical form.
+     This should be an idempotent function: if the name is already in
+     canonical form, it should be returned unchanged.
+
+
 .. attribute:: ConfigParser.SECTCRE

  A compiled regular expression used to parse section headers.  The default