BUG: properly convert PeriodIndex in to_datetime close pandas-dev#1703

Author: wesm

RELEASE.rst

@@ -81,6 +81,7 @@ pandas 0.8.2
   - Fix performance problem in infer_freq with lots of non-unique stamps (#1686)
   - Fix handling of PeriodIndex as argument to create MultiIndex (#1705)
   - Fix re: unicode MultiIndex level names in Series/DataFrame repr (#1736)
+  - Handle PeriodIndex in to_datetime instance method (#1703)
 
 pandas 0.8.1
 ============

pandas/core/index.py

@@ -150,8 +150,6 @@ def to_datetime(self, dayfirst=False):
             parser = lambda x: parse(x, dayfirst=dayfirst)
             parsed = lib.try_parse_dates(self.values, parser=parser)
             return DatetimeIndex(parsed)
-        elif isinstance(self, DatetimeIndex):
-            return self.copy()
         else:
             return DatetimeIndex(self.values)
 

pandas/tseries/index.py

@@ -499,6 +499,9 @@ def __contains__(self, key):
         except (KeyError, TypeError):
             return False
 
+    def to_datetime(self, dayfirst=False):
+        return self.copy()
+
     def groupby(self, f):
         objs = self.asobject
         return _algos.groupby_object(objs, f)

pandas/tseries/period.py

@@ -691,6 +691,9 @@ def asfreq(self, freq=None, how='E'):
         result.freq = freq
         return result
 
+    def to_datetime(self, dayfirst=False):
+        return self.to_timestamp()
+
     year = _field_accessor('year', 0)
     month = _field_accessor('month', 3)
     day = _field_accessor('day', 4)

pandas/tseries/tests/test_period.py

@@ -12,6 +12,7 @@
 
 from numpy.ma.testutils import assert_equal
 
+from pandas import Timestamp
 from pandas.tseries.frequencies import MONTHS, DAYS
 from pandas.tseries.period import Period, PeriodIndex, period_range
 from pandas.tseries.index import DatetimeIndex, date_range
@@ -1780,6 +1781,12 @@ def test_with_multi_index(self):
 
         self.assert_(isinstance(s.index.values[0][0], Period))
 
+    def test_to_datetime_1703(self):
+        index = period_range('1/1/2012',periods=4,freq='D')
+
+        result = index.to_datetime()
+        self.assertEquals(result[0], Timestamp('1/1/2012'))
+
 def _permute(obj):
     return obj.take(np.random.permutation(len(obj)))