[Python-checkins] r70031 - peps/trunk/pep-0372.txt

[raymond.hettinger]

Author: raymond.hettinger
Date: Fri Feb 27 22:23:56 2009
New Revision: 70031

Log:
Update notes on integration with ConfigParser and json.

Modified:
   peps/trunk/pep-0372.txt

Modified: peps/trunk/pep-0372.txt
==============================================================================
--- peps/trunk/pep-0372.txt	(original)
+++ peps/trunk/pep-0372.txt	Fri Feb 27 22:23:56 2009
@@ -181,7 +181,7 @@
    dbm) is likely a better fit.   It would be a mistake to try to be all
    things to all users.
 
-How well does odict work with the json module and PyYAML?
+How well does odict work with the json module, PyYAML, and ConfigParser?
 
    For json, the good news is that json's encoder respects odict's iteration order:
 
@@ -189,13 +189,15 @@
         >>> json.dumps(OrderedDict(items))
         '{"one": 1, "two": 2, "three": 3, "four": 4, "five": 5}'
 
-   The bad news is that the object_hook for json decoders will pass in an
-   already built dictionary so that the order is lost before the object
-   hook sees it:
+   In Py2.6, the object_hook for json decoders passes-in an already built
+   dictionary so order is lost before the object hook sees it.  This
+   problem is being fixed for Python 2.7/3.1 by adding an new hook that
+   preserves order (see http://bugs.python.org/issue5381 ).  
+   With the new hook, order can be preserved:
 
         >>> jtext = '{"one": 1, "two": 2, "three": 3, "four": 4, "five": 5}'
-        >>> json.loads(jtext, object_hook=OrderedDict)
-        OrderedDict({u'four': 4, u'three': 3, u'five': 5, u'two': 2, u'one': 1})
+        >>> json.loads(jtext, object_pairs_hook=OrderedDict)
+        OrderedDict({'one': 1, 'two': 2, 'three': 3, 'four': 4, 'five': 5})
 
    For PyYAML, a full round-trip is problem free:
 
@@ -211,6 +213,14 @@
         >>> yaml.load(ytext)
         OrderedDict({'one': 1, 'two': 2, 'three': 3, 'four': 4, 'five': 5})
 
+    For the ConfigParser module, round-tripping is problem free.  Custom
+    dicts were added in Py2.6 specifically to support ordered dictionaries:
+
+        >>> config = ConfigParser(dict_type=OrderedDict)
+        >>> config.read('myconfig.ini')
+        >>> config.remove_option('Log', 'error')
+        >>> config.write(open('myconfig.ini', 'w'))
+
 How does odict handle equality testing?
 
    Being a dict, one might expect equality tests to not care about order.  For