BUG: Period.__eq__ numpy scalar (pandas-dev#44182 (comment)) (pandas-dev#44285)

Author: mathause

pandas/_libs/tslibs/period.pyx

@@ -1657,8 +1657,12 @@ cdef class _Period(PeriodMixin):
         elif other is NaT:
             return _nat_scalar_rules[op]
         elif util.is_array(other):
-            # in particular ndarray[object]; see test_pi_cmp_period
-            return np.array([PyObject_RichCompare(self, x, op) for x in other])
+            # GH#44285
+            if cnp.PyArray_IsZeroDim(other):
+                return PyObject_RichCompare(self, other.item(), op)
+            else:
+                # in particular ndarray[object]; see test_pi_cmp_period
+                return np.array([PyObject_RichCompare(self, x, op) for x in other])
         return NotImplemented
 
     def __hash__(self):

pandas/tests/arithmetic/test_period.py

@@ -189,6 +189,10 @@ def test_pi_cmp_period(self):
         result = idx.values.reshape(10, 2) < idx[10]
         tm.assert_numpy_array_equal(result, exp.reshape(10, 2))
 
+        # Tests Period.__richcmp__ against ndarray[object, ndim=0]
+        result = idx < np.array(idx[10])
+        tm.assert_numpy_array_equal(result, exp)
+
     # TODO: moved from test_datetime64; de-duplicate with version below
     def test_parr_cmp_period_scalar2(self, box_with_array):
         xbox = get_expected_box(box_with_array)

pandas/tests/scalar/period/test_period.py

@@ -1148,6 +1148,16 @@ def test_period_cmp_nat(self):
             assert not left <= right
             assert not left >= right
 
+    @pytest.mark.parametrize(
+        "zerodim_arr, expected",
+        ((np.array(0), False), (np.array(Period("2000-01", "M")), True)),
+    )
+    def test_comparison_numpy_zerodim_arr(self, zerodim_arr, expected):
+        p = Period("2000-01", "M")
+
+        assert (p == zerodim_arr) is expected
+        assert (zerodim_arr == p) is expected
+
 
 class TestArithmetic:
     def test_sub_delta(self):