bpo-33504: Migrate configparser from OrderedDict to dict. (#6819)

With 3.7+, dictionary are ordered by design.  Configparser still uses
collections.OrderedDict, which is unnecessary.  This updates the module
to use the standard dict implementation by default, and changes the
docs and tests to match.

1 files changed, 9 insertions, 41 deletions

diff --git a/Doc/library/configparser.rst b/Doc/library/configparser.rst
index f51c580..5a2178f 100644
--- a/Doc/library/configparser.rst
+++ b/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``