ENH: Period comparisons with mismatched freq use py3 behavior (pandas-dev#39274)

Author: jbrockmendel

doc/source/whatsnew/v1.3.0.rst

@@ -322,7 +322,7 @@ I/O
 
 Period
 ^^^^^^
-
+- Comparisons of :class:`Period` objects or :class:`Index`, :class:`Series`, or :class:`DataFrame` with mismatched ``PeriodDtype`` now behave like other mismatched-type comparisons, returning ``False`` for equals, ``True`` for not-equal, and raising ``TypeError`` for inequality checks (:issue:`??`)
 -
 -
 

pandas/_libs/tslibs/period.pyx

@@ -1547,6 +1547,10 @@ cdef class _Period(PeriodMixin):
     def __richcmp__(self, other, op):
         if is_period_object(other):
             if other.freq != self.freq:
+                if op == Py_EQ:
+                    return False
+                elif op == Py_NE:
+                    return True
                 msg = DIFFERENT_FREQ.format(cls=type(self).__name__,
                                             own_freq=self.freqstr,
                                             other_freq=other.freqstr)

pandas/core/arrays/datetimelike.py

@@ -21,6 +21,7 @@
 from pandas._libs import algos, lib
 from pandas._libs.tslibs import (
     BaseOffset,
+    IncompatibleFrequency,
     NaT,
     NaTType,
     Period,
@@ -441,7 +442,7 @@ def _validate_comparison_value(self, other):
             try:
                 # GH#18435 strings get a pass from tzawareness compat
                 other = self._scalar_from_string(other)
-            except ValueError:
+            except (ValueError, IncompatibleFrequency):
                 # failed to parse as Timestamp/Timedelta/Period
                 raise InvalidComparison(other)
 
@@ -451,7 +452,7 @@ def _validate_comparison_value(self, other):
             other = self._scalar_type(other)  # type: ignore[call-arg]
             try:
                 self._check_compatible_with(other)
-            except TypeError as err:
+            except (TypeError, IncompatibleFrequency) as err:
                 # e.g. tzawareness mismatch
                 raise InvalidComparison(other) from err
 
@@ -465,7 +466,7 @@ def _validate_comparison_value(self, other):
             try:
                 other = self._validate_listlike(other, allow_object=True)
                 self._check_compatible_with(other)
-            except TypeError as err:
+            except (TypeError, IncompatibleFrequency) as err:
                 if is_object_dtype(getattr(other, "dtype", None)):
                     # We will have to operate element-wise
                     pass

pandas/tests/arithmetic/test_period.py

@@ -272,38 +272,38 @@ def test_parr_cmp_pi(self, freq, box_with_array):
         tm.assert_equal(base <= idx, exp)
 
     @pytest.mark.parametrize("freq", ["M", "2M", "3M"])
-    def test_parr_cmp_pi_mismatched_freq_raises(self, freq, box_with_array):
+    def test_parr_cmp_pi_mismatched_freq(self, freq, box_with_array):
         # GH#13200
         # different base freq
         base = PeriodIndex(["2011-01", "2011-02", "2011-03", "2011-04"], freq=freq)
         base = tm.box_expected(base, box_with_array)
 
-        msg = "Input has different freq=A-DEC from "
-        with pytest.raises(IncompatibleFrequency, match=msg):
+        msg = rf"Invalid comparison between dtype=period\[{freq}\] and Period"
+        with pytest.raises(TypeError, match=msg):
             base <= Period("2011", freq="A")
 
-        with pytest.raises(IncompatibleFrequency, match=msg):
+        with pytest.raises(TypeError, match=msg):
             Period("2011", freq="A") >= base
 
         # TODO: Could parametrize over boxes for idx?
         idx = PeriodIndex(["2011", "2012", "2013", "2014"], freq="A")
-        rev_msg = r"Input has different freq=(M|2M|3M) from PeriodArray\(freq=A-DEC\)"
+        rev_msg = r"Invalid comparison between dtype=period\[A-DEC\] and PeriodArray"
         idx_msg = rev_msg if box_with_array in [tm.to_array, pd.array] else msg
-        with pytest.raises(IncompatibleFrequency, match=idx_msg):
+        with pytest.raises(TypeError, match=idx_msg):
             base <= idx
 
         # Different frequency
-        msg = "Input has different freq=4M from "
-        with pytest.raises(IncompatibleFrequency, match=msg):
+        msg = rf"Invalid comparison between dtype=period\[{freq}\] and Period"
+        with pytest.raises(TypeError, match=msg):
             base <= Period("2011", freq="4M")
 
-        with pytest.raises(IncompatibleFrequency, match=msg):
+        with pytest.raises(TypeError, match=msg):
             Period("2011", freq="4M") >= base
 
         idx = PeriodIndex(["2011", "2012", "2013", "2014"], freq="4M")
-        rev_msg = r"Input has different freq=(M|2M|3M) from PeriodArray\(freq=4M\)"
+        rev_msg = r"Invalid comparison between dtype=period\[4M\] and PeriodArray"
         idx_msg = rev_msg if box_with_array in [tm.to_array, pd.array] else msg
-        with pytest.raises(IncompatibleFrequency, match=idx_msg):
+        with pytest.raises(TypeError, match=idx_msg):
             base <= idx
 
     @pytest.mark.parametrize("freq", ["M", "2M", "3M"])
@@ -354,12 +354,13 @@ def test_pi_cmp_nat_mismatched_freq_raises(self, freq):
         idx1 = PeriodIndex(["2011-01", "2011-02", "NaT", "2011-05"], freq=freq)
 
         diff = PeriodIndex(["2011-02", "2011-01", "2011-04", "NaT"], freq="4M")
-        msg = "Input has different freq=4M from Period(Array|Index)"
-        with pytest.raises(IncompatibleFrequency, match=msg):
+        msg = rf"Invalid comparison between dtype=period\[{freq}\] and PeriodArray"
+        with pytest.raises(TypeError, match=msg):
             idx1 > diff
 
-        with pytest.raises(IncompatibleFrequency, match=msg):
-            idx1 == diff
+        result = idx1 == diff
+        expected = np.array([False, False, False, False], dtype=bool)
+        tm.assert_numpy_array_equal(result, expected)
 
     # TODO: De-duplicate with test_pi_cmp_nat
     @pytest.mark.parametrize("dtype", [object, None])

pandas/tests/scalar/period/test_period.py

@@ -34,9 +34,7 @@ def test_construction(self):
         i4 = Period("2005", freq="M")
         i5 = Period("2005", freq="m")
 
-        msg = r"Input has different freq=M from Period\(freq=A-DEC\)"
-        with pytest.raises(IncompatibleFrequency, match=msg):
-            i1 != i4
+        assert i1 != i4
         assert i4 == i5
 
         i1 = Period.now("Q")
@@ -1071,11 +1069,9 @@ def test_comparison_mismatched_freq(self):
         jan = Period("2000-01", "M")
         day = Period("2012-01-01", "D")
 
+        assert not jan == day
+        assert jan != day
         msg = r"Input has different freq=D from Period\(freq=M\)"
-        with pytest.raises(IncompatibleFrequency, match=msg):
-            jan == day
-        with pytest.raises(IncompatibleFrequency, match=msg):
-            jan != day
         with pytest.raises(IncompatibleFrequency, match=msg):
             jan < day
         with pytest.raises(IncompatibleFrequency, match=msg):