Add OrderedDict support to collections.namedtuple().

Doc/library/collections.rst

@@ -651,9 +651,9 @@ Example:
            def __repr__(self):
                return 'Point(x=%r, y=%r)' % self
    <BLANKLINE>
-           def _asdict(t):
-               'Return a new dict which maps field names to their values'
-               return {'x': t[0], 'y': t[1]}
+           def _asdict(self):
+               'Return a new OrderedDict which maps field names to their values'
+               return OrderedDict(zip(self._fields, self))
    <BLANKLINE>
            def _replace(self, **kwds):
                'Return a new Point object replacing specified fields with new values'
@@ -711,10 +711,14 @@ field names, the method and attribute names start with an underscore.
 
 .. method:: somenamedtuple._asdict()
 
-   Return a new dict which maps field names to their corresponding values::
+   Return a new :class:`OrderedDict` which maps field names to their corresponding
+   values::
 
       >>> p._asdict()
-      {'x': 11, 'y': 22}
+      OrderedDict([('x', 11), ('y', 22)])
+
+   .. versionchanged 3.1
+      Returns an :class:`OrderedDict` instead of a regular :class:`dict`.
 
 .. method:: somenamedtuple._replace(kwargs)
 

Lib/collections.py

@@ -149,7 +149,6 @@ def namedtuple(typename, field_names, verbose=False, rename=False):
     numfields = len(field_names)
     argtxt = repr(field_names).replace("'", "")[1:-1]   # tuple repr without parens or quotes
     reprtxt = ', '.join('%s=%%r' % name for name in field_names)
-    dicttxt = ', '.join('%r: t[%d]' % (name, pos) for pos, name in enumerate(field_names))
     template = '''class %(typename)s(tuple):
         '%(typename)s(%(argtxt)s)' \n
         __slots__ = () \n
@@ -165,9 +164,9 @@ def namedtuple(typename, field_names, verbose=False, rename=False):
             return result \n
         def __repr__(self):
             return '%(typename)s(%(reprtxt)s)' %% self \n
-        def _asdict(t):
-            'Return a new dict which maps field names to their values'
-            return {%(dicttxt)s} \n
+        def _asdict(self):
+            'Return a new OrderedDict which maps field names to their values'
+            return OrderedDict(zip(self._fields, self)) \n
         def _replace(self, **kwds):
             'Return a new %(typename)s object replacing specified fields with new values'
             result = self._make(map(kwds.pop, %(field_names)r, self))
@@ -183,7 +182,8 @@ def namedtuple(typename, field_names, verbose=False, rename=False):
 
     # Execute the template string in a temporary namespace and
     # support tracing utilities by setting a value for frame.f_globals['__name__']
-    namespace = dict(itemgetter=_itemgetter, __name__='namedtuple_%s' % typename)
+    namespace = dict(itemgetter=_itemgetter, __name__='namedtuple_%s' % typename,
+                     OrderedDict=OrderedDict)
     try:
         exec(template, namespace)
     except SyntaxError as e:

Misc/NEWS

@@ -177,6 +177,8 @@ Library
 
 - PEP 372:  Added collections.OrderedDict().
 
+- The _asdict() for method for namedtuples now returns an OrderedDict().
+
 - Issue #1733986: Fixed mmap crash in accessing elements of second map object
   with same tagname but larger size than first map. (Windows)