Array ufunc multiplication

CHANGES

@@ -8,6 +8,9 @@ Pint Changelog
   (PR #1629)
 - Add new SI prefixes: ronna-, ronto-, quetta-, quecto-.
   (PR #1652)
+- Fixed bug causing operations between arrays of quantity scalars and quantity holding
+  array resulting in incorrect units.
+  (PR #1677)
 - Implementation for numpy.positive added for Quantity.
   (PR #1663)
 - Changed frequency to angular frequency in the docs.

pint/facets/numpy/numpy_func.py

@@ -171,31 +171,36 @@ def get_op_output_unit(unit_op, first_input_units, all_args=None, size=None):
     """
     all_args = all_args or []
 
-    if unit_op == "sum":
-        result_unit = (1 * first_input_units + 1 * first_input_units).units
-    elif unit_op == "mul":
+    def multiply_units(args):
         product = first_input_units._REGISTRY.parse_units("")
-        for x in all_args:
+        for x in args:
             if hasattr(x, "units"):
                 product *= x.units
-        result_unit = product
+            elif _is_sequence_with_quantity_elements(x):
+                product *= x[0].units
+        return product
+
+    def get_numerator_unit(arg):
+        if _is_sequence_with_quantity_elements(arg):
+            return getattr(arg[0], "units", first_input_units._REGISTRY.parse_units(""))
+        else:
+            return getattr(arg, "units", first_input_units._REGISTRY.parse_units(""))
+
+    if unit_op == "sum":
+        result_unit = (1 * first_input_units + 1 * first_input_units).units
+    elif unit_op == "mul":
+        result_unit = multiply_units(all_args)
     elif unit_op == "delta":
         result_unit = (1 * first_input_units - 1 * first_input_units).units
     elif unit_op == "delta,div":
-        product = (1 * first_input_units - 1 * first_input_units).units
-        for x in all_args[1:]:
-            if hasattr(x, "units"):
-                product /= x.units
-        result_unit = product
+        numerator_unit = (1 * first_input_units - 1 * first_input_units).units
+        denominator_unit = multiply_units(all_args[1:])
+        result_unit = numerator_unit / denominator_unit
     elif unit_op == "div":
         # Start with first arg in numerator, all others in denominator
-        product = getattr(
-            all_args[0], "units", first_input_units._REGISTRY.parse_units("")
-        )
-        for x in all_args[1:]:
-            if hasattr(x, "units"):
-                product /= x.units
-        result_unit = product
+        numerator_unit = get_numerator_unit(all_args[0])
+        denominator_unit = multiply_units(all_args[1:])
+        result_unit = numerator_unit / denominator_unit
     elif unit_op == "variance":
         result_unit = ((1 * first_input_units + 1 * first_input_units) ** 2).units
     elif unit_op == "square":
@@ -212,13 +217,9 @@ def get_op_output_unit(unit_op, first_input_units, all_args=None, size=None):
         result_unit = first_input_units**size
     elif unit_op == "invdiv":
         # Start with first arg in numerator, all others in denominator
-        product = getattr(
-            all_args[0], "units", first_input_units._REGISTRY.parse_units("")
-        )
-        for x in all_args[1:]:
-            if hasattr(x, "units"):
-                product /= x.units
-        result_unit = product**-1
+        numerator_unit = get_numerator_unit(all_args[0])
+        denominator_unit = multiply_units(all_args[1:])
+        result_unit = (numerator_unit / denominator_unit) ** -1
     else:
         raise ValueError("Output unit method {} not understood".format(unit_op))
 

pint/testsuite/test_issues.py

@@ -886,6 +886,15 @@ def test_issue_1300(self):
         m = module_registry.Measurement(1, 0.1, "meter")
         assert m.default_format == "~P"
 
+    @helpers.requires_numpy()
+    def test_issue1674(self, module_registry):
+        Q_ = module_registry.Quantity
+        arr_of_q = np.array([Q_(2, "m"), Q_(4, "m")], dtype="object")
+        q_arr = Q_(np.array([1, 2]), "m")
+
+        helpers.assert_quantity_almost_equal(arr_of_q * q_arr, Q_([2, 8], "m^2"))
+        helpers.assert_quantity_almost_equal(arr_of_q / q_arr, Q_([2, 2], ""))
+
 
 if np is not None: