BUG: Series.apply fails on empty Series #2815

Author: changhiskhan

pandas/core/series.py

@@ -2286,6 +2286,9 @@ def apply(self, func, convert_dtype=True, args=(), **kwds):
         -------
         y : Series or DataFrame if func returns a Series
         """
+        if len(self) == 0:
+            return Series()
+
         if kwds or args and not isinstance(func, np.ufunc):
             f = lambda x: func(x, *args, **kwds)
         else:

pandas/tests/test_series.py

@@ -2685,6 +2685,16 @@ def test_apply(self):
         expected = DataFrame({'x': self.ts, 'x^2': self.ts ** 2})
         tm.assert_frame_equal(result, expected)
 
+        # empty series
+        s = Series()
+        rs = s.apply(lambda x: x)
+        tm.assert_series_equal(s, rs)
+
+        # index but no data
+        s = Series(index=[1,2,3])
+        rs = s.apply(lambda x: x)
+        tm.assert_series_equal(s, rs)
+
     def test_apply_same_length_inference_bug(self):
         s = Series([1, 2])
         f = lambda x: (x, x + 1)