BUG: Period.__eq__ numpy scalar (#44182 (comment))

pandas/_libs/tslibs/period.pyx

@@ -1656,7 +1656,7 @@ cdef class _Period(PeriodMixin):
             return PyObject_RichCompareBool(self.ordinal, other.ordinal, op)
         elif other is NaT:
             return _nat_scalar_rules[op]
-        elif util.is_array(other):
+        elif util.is_array(other) and not np.ndim(other) == 0:
             # in particular ndarray[object]; see test_pi_cmp_period
             return np.array([PyObject_RichCompare(self, x, op) for x in other])
         return NotImplemented

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(
+        "scalar, expected", ((np.array(0), np.bool_(False)), (np.int_(0), False))
+    )
+    def test_comparison_numpy_scalar(self, scalar, expected):
+        p = Period("2000-01", "M")
+
+        for left, right in ((p, scalar), (scalar, p)):
+            assert not left == right
+            assert (left == right) is expected
+
 
 class TestArithmetic:
     def test_sub_delta(self):