BUG: raise exception on NaT in DatetimeIndex.astype('O') #1340

Author: Chang She

pandas/tseries/index.py

@@ -5,6 +5,7 @@
 
 import numpy as np
 
+from pandas.core.common import isnull
 from pandas.core.index import Index, Int64Index
 from pandas.tseries.frequencies import infer_freq, to_offset
 from pandas.tseries.offsets import DateOffset, generate_range, Tick
@@ -513,6 +514,9 @@ def astype(self, dtype):
         dtype = np.dtype(dtype)
 
         if dtype == np.object_:
+            if isnull(self).any():
+                msg = 'DatetimeIndex with NaT cannot be converted to object'
+                raise ValueError(msg)
             return self.asobject
         return Index.astype(self, dtype)
 

pandas/tseries/tests/test_timeseries.py

@@ -945,6 +945,10 @@ def test_index_conversion(self):
 
         self.assertRaises(ValueError, DatetimeIndex, ['a', 'b', 'c', 'd'])
 
+    def test_object_convert_fail(self):
+        idx = DatetimeIndex([NaT])
+        self.assertRaises(ValueError, idx.astype, 'O')
+
     def test_setops_conversion_fail(self):
         index = self.frame.index