BUG: make Series.tz_localize work with length-0 non-DatetimeIndex. close pandas-dev#2248

Author: wesm

RELEASE.rst

@@ -110,6 +110,7 @@ pandas 0.9.1
   - Fix issue constructing DataFrame from empty Series with name (#2234)
   - Use console-width detection in interactive sessions only (#1610)
   - Fix parallel_coordinates legend bug with mpl 1.2.0 (#2237)
+  - Make tz_localize work in corner case of empty Series (#2248)
 
 pandas 0.9.0
 ============

pandas/core/series.py

@@ -2756,7 +2756,15 @@ def tz_localize(self, tz, copy=True):
         -------
         localized : TimeSeries
         """
-        new_index = self.index.tz_localize(tz)
+        from pandas.tseries.index import DatetimeIndex
+
+        if not isinstance(self.index, DatetimeIndex):
+            if len(self.index) > 0:
+                raise Exception('Cannot tz-localize non-time series')
+
+            new_index = DatetimeIndex([], tz=tz)
+        else:
+            new_index = self.index.tz_localize(tz)
 
         new_values = self.values
         if copy:

pandas/tseries/index.py

@@ -203,6 +203,10 @@ def __new__(cls, data=None,
                 if isinstance(data, DatetimeIndex):
                     if name is not None:
                         data.name = name
+
+                    if tz is not None:
+                        return data.tz_localize(tz)
+
                     return data
 
         if issubclass(data.dtype.type, basestring):

pandas/tseries/tests/test_timezones.py

@@ -137,6 +137,17 @@ def test_tz_localize_dti(self):
                             freq='L')
         self.assertRaises(pytz.NonExistentTimeError, dti.tz_localize, 'US/Eastern')
 
+    def test_tz_localize_empty_series(self):
+        # #2248
+
+        ts = Series()
+
+        ts2 = ts.tz_localize('utc')
+        self.assertTrue(ts2.index.tz == pytz.utc)
+
+        ts2 = ts.tz_localize('US/Eastern')
+        self.assertTrue(ts2.index.tz == pytz.timezone('US/Eastern'))
+
     def test_astimezone(self):
         utc = Timestamp('3/11/2012 22:00', tz='UTC')
         expected = utc.tz_convert('US/Eastern')