PEP 416: add a section about dictproxy, add more links to Python recipes

pep-0416.txt

@@ -108,15 +108,43 @@ hash(frozendict) raises a TypeError if a value is not hashable. Freezing an
 object is not the purpose of this PEP.
 
 
+Alternative: dictproxy
+======================
+
+Python has a builtin dictproxy type used by type.__dict__ getter descriptor.
+This type is not public. dictproxy is a read-only view of a dictionary, but it
+is not read-only mapping.  If a dictionary is modified, the dictproxy is also
+modified.
+
+dictproxy can be used using ctypes and the Python C API, see for example the
+`make dictproxy object via ctypes.pythonapi and type() (Python recipe 576540)`_
+by Ikkei Shimomura. The recipe contains a test checking that a dictproxy is
+"mutable" (modify the dictionary linked to the dictproxy).
+
+However dictproxy can be useful in some cases, where its mutable property is
+not an issue, to avoid a copy of the dictionary.
+
+
 Links
 =====
 
+ * `Issue #14162: PEP 416: Add a builtin frozendict type
+   <http://bugs.python.org/issue14162>`_
  * PEP 412: Key-Sharing Dictionary
    (`issue #13903 <http://bugs.python.org/issue13903>`_)
  * PEP 351: The freeze protocol
  * `The case for immutable dictionaries; and the central misunderstanding of PEP 351 <http://www.cs.toronto.edu/~tijmen/programming/immutableDictionaries.html>`_
- * `Frozen dictionaries (Python recipe 414283) <http://code.activestate.com/recipes/414283-frozen-dictionaries/>`_
-   by Oren Tirosh
+ * `Frozen dictionaries (Python recipe 414283) <http://code.activestate.com/recipes/414283/>`_
+   by Oren Tirosh. Blacklist approach: inherit from dict and override write
+   methods to raise an exception. It is not truly read-only: it is still
+   possible to call dict methods on such "frozen dictionary" to modify it.
+ * `Implementing an Immutable Dictionary (Python recipe 498072) <http://code.activestate.com/recipes/498072/>`_
+   by Aristotelis Mikropoulos. Similar to frozendict except that it is not
+   truly read-only. It is possible to access to this private internal dict.
+   It does not implement __hash__ and has an implementation issue: it is
+   possible to call again __init__() to modify the mapping.
+ * `make dictproxy object via ctypes.pythonapi and type() (Python recipe
+   576540) <http://code.activestate.com/recipes/576540/>`_ by Ikkei Shimomura.
  * Python security modules implementing read-only object proxies using a C
    extension: