bpo-34003: Use dict instead of OrderedDict in csv.DictReader (GH-8014)

Author: selik

Doc/library/csv.rst

@@ -150,12 +150,12 @@ The :mod:`csv` module defines the following classes:
  dialect='excel', *args, **kwds)
 
  Create an object that operates like a regular reader but maps the
- information in each row to an :mod:`OrderedDict <collections.OrderedDict>`
- whose keys are given by the optional *fieldnames* parameter.
+ information in each row to a :class:`dict` whose keys are given by the
+ optional *fieldnames* parameter.
 
  The *fieldnames* parameter is a :term:`sequence`. If *fieldnames* is
  omitted, the values in the first row of file *f* will be used as the
- fieldnames. Regardless of how the fieldnames are determined, the ordered
+ fieldnames. Regardless of how the fieldnames are determined, the
  dictionary preserves their original ordering.
 
  If a row has more fields than fieldnames, the remaining data is put in a
@@ -166,8 +166,8 @@ The :mod:`csv` module defines the following classes:
  All other optional or keyword arguments are passed to the underlying
  :class:`reader` instance.
 
- .. versionchanged:: 3.6
- Returned rows are now of type :class:`OrderedDict`.
+ .. versionchanged:: 3.8
+ Returned rows are now of type :class:`dict`.
 
  A short usage example::
 
@@ -181,7 +181,7 @@ The :mod:`csv` module defines the following classes:
  John Cleese
 
  >>> print(row)
- OrderedDict([('first_name', 'John'), ('last_name', 'Cleese')])
+ {'first_name': 'John', 'last_name': 'Cleese'}
 
 
 .. class:: DictWriter(f, fieldnames, restval='', extrasaction='raise', \

Lib/csv.py

@@ -11,7 +11,6 @@
  __doc__
 from _csv import Dialect as _Dialect
 
-from collections import OrderedDict
 from io import StringIO
 
 __all__ = ["QUOTE_MINIMAL", "QUOTE_ALL", "QUOTE_NONNUMERIC", "QUOTE_NONE",
@@ -117,7 +116,7 @@ def __next__(self):
  # values
  while row == []:
  row = next(self.reader)
- d = OrderedDict(zip(self.fieldnames, row))
+ d = dict(zip(self.fieldnames, row))
  lf = len(self.fieldnames)
  lr = len(row)
  if lf < lr:

Misc/NEWS.d/next/Library/2018-06-29-13-05-01.bpo-34003.Iu831h.rst

@@ -0,0 +1,2 @@
+csv.DictReader now creates dicts instead of OrderedDicts. Patch by Michael
+Selik.