Add 'records' outtype to to_dict method.

Author: tshauck

doc/source/release.rst

@@ -47,6 +47,8 @@ pandas 0.13
   - Added a more informative error message when plot arguments contain
     overlapping color and style arguments (:issue:`4402`)
   - Significant table writing performance improvements in ``HDFStore``
+  - ``to_dict`` now takes ``records`` as a possible outtype.  Returns an array
+    of column-keyed dictionaries. (:pullrequest:`4936`)
 
 **API Changes**
 

doc/source/v0.13.0.txt

@@ -81,6 +81,8 @@ Enhancements
   - Clipboard functionality now works with PySide (:issue:`4282`)
   - Added a more informative error message when plot arguments contain
     overlapping color and style arguments (:issue:`4402`)
+  - ``to_dict`` now takes ``records`` as a possible outtype.  Returns an array
+    of column-keyed dictionaries. (:pullrequest:`4936`)
 
 Bug Fixes
 ~~~~~~~~~

pandas/core/frame.py

@@ -962,11 +962,11 @@ def to_dict(self, outtype='dict'):
 
         Parameters
         ----------
-        outtype : str {'dict', 'list', 'series'}
+        outtype : str {'dict', 'list', 'series', 'records'}
             Determines the type of the values of the dictionary. The
             default `dict` is a nested dictionary {column -> {index -> value}}.
             `list` returns {column -> list(values)}. `series` returns
-            {column -> Series(values)}.
+            {column -> Series(values)}. `records` returns [{columns -> value}].
             Abbreviations are allowed.
 
 
@@ -983,6 +983,9 @@ def to_dict(self, outtype='dict'):
             return dict((k, v.tolist()) for k, v in compat.iteritems(self))
         elif outtype.lower().startswith('s'):
             return dict((k, v) for k, v in compat.iteritems(self))
+        elif outtype.lower().startswith('r'):
+            return [dict((k, v) for k, v in zip(self.columns, row)) \
+                    for row in self.values]
         else:  # pragma: no cover
             raise ValueError("outtype %s not understood" % outtype)
 

pandas/tests/test_frame.py

@@ -3396,6 +3396,14 @@ def test_to_dict(self):
             for k2, v2 in compat.iteritems(v):
                 self.assertEqual(v2, recons_data[k][k2])
 
+        recons_data = DataFrame(test_data).to_dict("r")
+
+        expected_records = [{'A': 1.0, 'B': '1'},
+                            {'A': 2.0, 'B': '2'},
+                            {'A': nan, 'B': '3'}]
+
+        tm.assert_almost_equal(recons_data, expected_records)
+
     def test_to_records_dt64(self):
         df = DataFrame([["one", "two", "three"],
                         ["four", "five", "six"]],