Quantity comparisons ensure other is Quantity.

3 files changed, 24 insertions, 3 deletions

diff --git a/pint/quantity.py b/pint/quantity.py
index 0395a65..92cb81b 100644
--- a/pint/quantity.py
+++ b/pint/quantity.py
@@ -1577,7 +1577,7 @@ class Quantity(PrettyIPython, SharedRegistryObject):
 
     @check_implemented
     def compare(self, other, op):
-        if not isinstance(other, self.__class__):
+        if not isinstance(other, Quantity):
             if self.dimensionless:
                 return op(
                     self._convert_magnitude_not_inplace(self.UnitsContainer()), other
@@ -1598,6 +1598,14 @@ class Quantity(PrettyIPython, SharedRegistryObject):
             else:
                 raise ValueError("Cannot compare Quantity and {}".format(type(other)))
 
+
+        # Registry equality check based on util.SharedRegistryObject
+        if self._REGISTRY is not other._REGISTRY:
+            mess = "Cannot operate with {} and {} of different registries."
+            raise ValueError(
+                mess.format(self.__class__.__name__, other.__class__.__name__)
+                )
+
         if self._units == other._units:
             return op(self._magnitude, other._magnitude)
         if self.dimensionality != other.dimensionality:
diff --git a/pint/testsuite/test_measurement.py b/pint/testsuite/test_measurement.py
index b5acff0..5ebb33b 100644
--- a/pint/testsuite/test_measurement.py
+++ b/pint/testsuite/test_measurement.py
@@ -86,7 +86,7 @@ class TestMeasurement(QuantityTestCase):
             ("{:.3uL}", r"\left(0.2000 \pm 0.0100\right)\ \mathrm{second}^{2}"),
             ("{:.3uH}", "(0.2000 &plusmn; 0.0100) second<sup>2</sup>"),
             ("{:.3uC}", "(0.2000+/-0.0100) second**2"),
-            ("{:.3uLx}", r"\SI{0.2000 +- 0.0100}{\second\squared}",),
+            ("{:.3uLx}", r"\SI{0.2000 +- 0.0100}{\second\squared}"),
             ("{:.1uLx}", r"\SI{0.20 +- 0.01}{\second\squared}"),
         ):
             with self.subTest(spec):
@@ -236,3 +236,9 @@ class TestMeasurement(QuantityTestCase):
                 r.value.magnitude, ml.value.magnitude / mr.value.magnitude
             )
             self.assertEqual(r.value.units, ml.value.units / mr.value.units)
+
+    def test_measurement_comparison(self):
+        x = self.Q_(4.2, "meter")
+        y = self.Q_(5.0, "meter").plus_minus(0.1)
+        self.assertTrue(x<=y)
+        self.assertFalse(x>=y)
diff --git a/pint/testsuite/test_quantity.py b/pint/testsuite/test_quantity.py
index b5780e5..fe86801 100644
--- a/pint/testsuite/test_quantity.py
+++ b/pint/testsuite/test_quantity.py
@@ -6,7 +6,7 @@ import pickle
 import warnings
 from unittest.mock import patch
 
-from pint import DimensionalityError, OffsetUnitCalculusError, UnitRegistry
+from pint import DimensionalityError, OffsetUnitCalculusError, UnitRegistry, Quantity, get_application_registry
 from pint.compat import np
 from pint.testsuite import QuantityTestCase, helpers
 from pint.testsuite.parameterized import ParameterizedTestCase
@@ -63,6 +63,8 @@ class TestQuantity(QuantityTestCase):
         y = self.Q_(4.2, "meter")
         z = self.Q_(5, "meter")
         j = self.Q_(5, "meter*meter")
+        k = 5 * get_application_registry().meter # Include a comparison to the application registry
+        l = Quantity(5, "meter") # Include a comparison to a directly created Quantity
 
         # identity for single object
         self.assertTrue(x == x)
@@ -81,6 +83,11 @@ class TestQuantity(QuantityTestCase):
         self.assertTrue(x != z)
         self.assertTrue(x < z)
 
+        # Compare with items to the separate application registry
+        self.assertTrue(k >= l) # These should both be from application registry
+        with self.assertRaises(ValueError):
+            z>l # One from local registry, one from application registry
+
         self.assertTrue(z != j)
 
         self.assertNotEqual(z, j)