bpo-33504: Migrate configparser from OrderedDict to dict.

Doc/library/configparser.rst

@@ -445,20 +445,19 @@ the :meth:`__init__` options:
   Hint: if you want to specify default values for a specific section, use
   :meth:`read_dict` before you read the actual file.
 
-* *dict_type*, default value: :class:`collections.OrderedDict`
+* *dict_type*, default value: :class:`dict`
 
   This option has a major impact on how the mapping protocol will behave and how
-  the written configuration files look.  With the default ordered
-  dictionary, every section is stored in the order they were added to the
-  parser.  Same goes for options within sections.
+  the written configuration files look.  With the standard dictionary, every
+  section is stored in the order they were added to the parser.  Same goes for
+  options within sections.
 
   An alternative dictionary type can be used for example to sort sections and
-  options on write-back.  You can also use a regular dictionary for performance
-  reasons.
+  options on write-back.
 
   Please note: there are ways to add a set of key-value pairs in a single
   operation.  When you use a regular dictionary in those operations, the order
-  of the keys may be random.  For example:
+  of the keys will be ordered.  For example:
 
   .. doctest::
 
@@ -474,40 +473,9 @@ the :meth:`__init__` options:
      ...                                'baz': 'z'}
      ... })
      >>> parser.sections()  # doctest: +SKIP
-     ['section3', 'section2', 'section1']
-     >>> [option for option in parser['section3']] # doctest: +SKIP
-     ['baz', 'foo', 'bar']
-
-  In these operations you need to use an ordered dictionary as well:
-
-  .. doctest::
-
-     >>> from collections import OrderedDict
-     >>> parser = configparser.ConfigParser()
-     >>> parser.read_dict(
-     ...   OrderedDict((
-     ...     ('s1',
-     ...      OrderedDict((
-     ...        ('1', '2'),
-     ...        ('3', '4'),
-     ...        ('5', '6'),
-     ...      ))
-     ...     ),
-     ...     ('s2',
-     ...      OrderedDict((
-     ...        ('a', 'b'),
-     ...        ('c', 'd'),
-     ...        ('e', 'f'),
-     ...      ))
-     ...     ),
-     ...   ))
-     ... )
-     >>> parser.sections()  # doctest: +SKIP
-     ['s1', 's2']
-     >>> [option for option in parser['s1']]  # doctest: +SKIP
-     ['1', '3', '5']
-     >>> [option for option in parser['s2'].values()]  # doctest: +SKIP
-     ['b', 'd', 'f']
+     ['section1', 'section2', 'section3']
+     >>> [option for option in parser['section3']]  # doctest: +SKIP
+     ['foo', 'bar', 'baz']
 
 * *allow_no_value*, default value: ``False``
 

Lib/configparser.py

@@ -139,7 +139,7 @@
 """
 
 from collections.abc import MutableMapping
-from collections import OrderedDict as _default_dict, ChainMap as _ChainMap
+from collections import ChainMap as _ChainMap
 import functools
 import io
 import itertools
@@ -157,6 +157,7 @@
            "LegacyInterpolation", "SectionProxy", "ConverterMapping",
            "DEFAULTSECT", "MAX_INTERPOLATION_DEPTH"]
 
+_default_dict = dict
 DEFAULTSECT = "DEFAULT"
 
 MAX_INTERPOLATION_DEPTH = 10

Lib/test/test_configparser.py

@@ -1109,7 +1109,7 @@ def test_set_nonstring_types(self):
         self.assertEqual(cf.get(123, 'this is sick'), True)
         if cf._dict is configparser._default_dict:
             # would not work for SortedDict; only checking for the most common
-            # default dictionary (OrderedDict)
+            # default dictionary (dict)
             cf.optionxform = lambda x: x
             cf.set('non-string', 1, 1)
             self.assertEqual(cf.get('non-string', 1), 1)

Misc/ACKS

@@ -1310,6 +1310,7 @@ Marc Recht
 John Redford
 Terry J. Reedy
 Gareth Rees
+John Reese
 Steve Reeves
 Lennart Regebro
 John Regehr

Misc/NEWS.d/next/Library/2018-05-15-12-11-13.bpo-33504.czsHFg.rst

@@ -0,0 +1,2 @@
+Switch the default dictionary implementation for :mod:`configparser` from
+:class:`collections.OrderedDict` to the standard :class:`dict` type.