Adds default_units to Property

Author: Maxcode123

src/property_utils/properties/property.py

@@ -3,7 +3,7 @@
 """
 
 from dataclasses import dataclass, replace
-from typing import Type, Optional
+from typing import Type, Optional, ClassVar
 from math import isclose
 
 try:
@@ -63,17 +63,23 @@ class Property:
     value: float
     unit: UnitDescriptor
     unit_converter: Optional[Type[UnitConverter]] = None
+    default_units: ClassVar[Optional[UnitDescriptor]] = None
 
-    def __init__(self, value: float, unit: UnitDescriptor) -> None:
+    def __init__(self, value: float, unit: Optional[UnitDescriptor] = None) -> None:
         if not isinstance(value, (float, int)):
             raise PropertyValidationError(
                 f"cannot create Property; invalid 'value': {value}; expected numeric. "
             )
+
+        if unit is None and self.default_units is not None:
+            unit = self.default_units
+
         if not isinstance(unit, (MeasurementUnit, Dimension, CompositeDimension)):
             raise PropertyValidationError(
                 f"cannot create Property; invalid 'unit': {unit}. Expected an instance"
                 " of one of: MeasurementUnit, Dimension, CompositeDimension. "
             )
+
         self.value = value
         self.unit = unit
 

src/property_utils/tests/properties/test_property.py

@@ -3,7 +3,6 @@
 from unittest_extensions import args, TestCase
 
 from property_utils.properties.property import Property, p
-from property_utils.units.descriptors import CompositeDimension
 from property_utils.units.units import NonDimensionalUnit, PressureUnit
 from property_utils.exceptions.properties.property import (
     PropertyExponentError,
@@ -14,8 +13,9 @@
     Unit3,
     Unit4,
     Unit6,
-    Unit7,
     Unit8,
+    PropUnit1,
+    PropUnit2,
     generic_dimension_1,
     generic_composite_dimension,
 )
@@ -67,6 +67,30 @@ def test_does_not_initialize_converter(self):
         self.assertIsNone(self.result().unit_converter)
 
 
+@add_to(property_test_suite)
+class TestPropertyDefaultUnits(TestProperty):
+    def subject(self, **kwargs):
+        return PropUnit1(**kwargs)
+
+    @args({"value": 1, "unit": Unit1.A})
+    def test_with_units(self):
+        self.assert_result("1 A")
+
+    @args({"value": 1})
+    def test_with_no_units(self):
+        self.assert_result("1 a")
+
+
+@add_to(property_test_suite)
+class TestPropertyWithoutDefaultUnits(TestProperty):
+    def subject(self, value):
+        return PropUnit2(value)
+
+    @args({"value": 10})
+    def test_raises_validation_error(self):
+        self.assert_validation_error()
+
+
 @add_to(property_test_suite)
 class TestPropertyConstructor(TestCase):
     def subject(self, **kwargs):