BUG: DTI/TDI.equals with i8 (#36744)

Author: jbrockmendel

doc/source/whatsnew/v1.2.0.rst

@@ -305,7 +305,7 @@ Datetimelike
 - Bug in :meth:`DatetimeIndex.searchsorted`, :meth:`TimedeltaIndex.searchsorted`, :meth:`PeriodIndex.searchsorted`, and :meth:`Series.searchsorted` with ``datetime64``, ``timedelta64`` or ``Period`` dtype placement of ``NaT`` values being inconsistent with ``NumPy`` (:issue:`36176`, :issue:`36254`)
 - Inconsistency in :class:`DatetimeArray`, :class:`TimedeltaArray`, and :class:`PeriodArray`  setitem casting arrays of strings to datetimelike scalars but not scalar strings (:issue:`36261`)
 - Bug in :class:`DatetimeIndex.shift` incorrectly raising when shifting empty indexes (:issue:`14811`)
-
+- Bug in :meth:`DatetimeIndex.equals` and :meth:`TimedeltaIndex.equals` incorrectly considering ``int64`` indexes as equal (:issue:`36744`)
 
 Timedelta
 ^^^^^^^^^

pandas/core/indexes/datetimelike.py

@@ -134,6 +134,8 @@ def equals(self, other: object) -> bool:
 
         if not isinstance(other, Index):
             return False
+        elif other.dtype.kind in ["f", "i", "u", "c"]:
+            return False
         elif not isinstance(other, type(self)):
             try:
                 other = type(self)(other)

pandas/core/ops/__init__.py

@@ -539,7 +539,9 @@ def _should_reindex_frame_op(
     if fill_value is None and level is None and axis is default_axis:
         # TODO: any other cases we should handle here?
         cols = left.columns.intersection(right.columns)
-        if not (cols.equals(left.columns) and cols.equals(right.columns)):
+
+        if len(cols) and not (cols.equals(left.columns) and cols.equals(right.columns)):
+            # TODO: is there a shortcut available when len(cols) == 0?
             return True
 
     return False

pandas/tests/computation/test_eval.py

@@ -1054,15 +1054,15 @@ def test_complex_series_frame_alignment(self, engine, parser):
                     m2, n, data_gen_f=f, r_idx_type=r2, c_idx_type=c2
                 )
                 index = getattr(locals().get(obj_name), index_name)
-                s = Series(np.random.randn(n), index[:n])
+                ser = Series(np.random.randn(n), index[:n])
 
                 if r2 == "dt" or c2 == "dt":
                     if engine == "numexpr":
-                        expected2 = df2.add(s)
+                        expected2 = df2.add(ser)
                     else:
-                        expected2 = df2 + s
+                        expected2 = df2 + ser
                 else:
-                    expected2 = df2 + s
+                    expected2 = df2 + ser
 
                 if r1 == "dt" or c1 == "dt":
                     if engine == "numexpr":
@@ -1072,11 +1072,11 @@ def test_complex_series_frame_alignment(self, engine, parser):
                 else:
                     expected = expected2 + df
 
-                if should_warn(df2.index, s.index, df.index):
+                if should_warn(df2.index, ser.index, df.index):
                     with tm.assert_produces_warning(RuntimeWarning):
-                        res = pd.eval("df2 + s + df", engine=engine, parser=parser)
+                        res = pd.eval("df2 + ser + df", engine=engine, parser=parser)
                 else:
-                    res = pd.eval("df2 + s + df", engine=engine, parser=parser)
+                    res = pd.eval("df2 + ser + df", engine=engine, parser=parser)
                 assert res.shape == expected.shape
                 tm.assert_frame_equal(res, expected)
 

pandas/tests/indexes/datetimelike.py

@@ -108,3 +108,10 @@ def test_getitem_preserves_freq(self):
 
         result = index[:]
         assert result.freq == index.freq
+
+    def test_not_equals_numeric(self):
+        index = self.create_index()
+
+        assert not index.equals(pd.Index(index.asi8))
+        assert not index.equals(pd.Index(index.asi8.astype("u8")))
+        assert not index.equals(pd.Index(index.asi8).astype("f8"))