BUG: fixed index power operation

* The power operation on a range of indexes was fixed. See issue #14973

Author: kamal94

doc/source/whatsnew/v0.20.0.txt

@@ -282,6 +282,7 @@ Performance Improvements
 Bug Fixes
 ~~~~~~~~~
 
+- Bug in ``Indexes`` Power numerical operations did not operate correctly (:issue:`14973`)
 - Bug in ``TimedeltaIndex`` addition where overflow was being allowed without error (:issue:`14816`)
 - Bug in ``DataFrame`` construction in which unsigned 64-bit integer elements were being converted to objects (:issue:`14881`)
 - Bug in ``astype()`` where ``inf`` values were incorrectly converted to integers. Now raises error now with ``astype()`` for Series and DataFrames (:issue:`14265`)

pandas/indexes/base.py

@@ -3534,7 +3534,9 @@ def _evaluate_numeric_binop(self, other):
             operator.sub, '__sub__', reversed=True)
         cls.__mul__ = cls.__rmul__ = _make_evaluate_binop(
             operator.mul, '__mul__')
-        cls.__pow__ = cls.__rpow__ = _make_evaluate_binop(
+        cls.__rpow__ = _make_evaluate_binop(
+            operator.pow, '__pow__', reversed=True)
+        cls.__pow__ = _make_evaluate_binop(
             operator.pow, '__pow__')
         cls.__mod__ = _make_evaluate_binop(
             operator.mod, '__mod__')

pandas/tests/indexes/test_numeric.py

@@ -105,6 +105,21 @@ def test_numeric_compat(self):
         for r, e in zip(result, expected):
             tm.assert_index_equal(r, e)
 
+        #test power calculations both ways
+        num_range = np.arange(1,11)
+        pow_range = 2.0**num_range
+        idxs = pd.Float64Index(range(1, 11))
+
+        expected_pow_values = pd.Float64Index(pow_range)
+        actual_pow_values = 2.0**idxs
+        tm.assert_index_equal(expected_pow_values, actual_pow_values)
+
+        pow_range_rev = num_range**2.0
+        expected_rev_pow_values = pd.Float64Index(pow_range_rev)
+        actual_rev_pow_values = idxs**2.0
+        tm.assert_index_equal(expected_rev_pow_values, actual_rev_pow_values)
+
+        
     def test_explicit_conversions(self):
 
         # GH 8608