Issue 12086: add example showing how to use name mangling.
diff --git a/Doc/tutorial/classes.rst b/Doc/tutorial/classes.rst
index a328ab2..bf1e26e 100644
--- a/Doc/tutorial/classes.rst
+++ b/Doc/tutorial/classes.rst
@@ -595,6 +595,28 @@
without regard to the syntactic position of the identifier, as long as it
occurs within the definition of a class.
+Name mangling is helpful for letting subclasses override methods without
+breaking intraclass method calls. For example::
+
+ class Mapping:
+ def __init__(self, iterable):
+ self.items_list = []
+ self.__update(iterable)
+
+ def update(self, iterable):
+ for item in iterable:
+ self.items_list.append(item)
+
+ __update = update # private copy of original update() method
+
+ class MappingSubclass(Mapping):
+
+ def update(self, keys, values):
+ # provides new signature for update()
+ # but does not break __init__()
+ for item in zip(keys, values):
+ self.items_list.append(item)
+
Note that the mangling rules are designed mostly to avoid accidents; it still is
possible to access or modify a variable that is considered private. This can
even be useful in special circumstances, such as in the debugger.