Add abs() support for quantities (#516)

Author: Marenz

RELEASE_NOTES.md

@@ -13,6 +13,7 @@
 ## New Features
 
 - Add quantity class `Frequency` for frequency values.
+- Add `abs()` support for quantities.
 
 ## Bug Fixes
 

src/frequenz/sdk/timeseries/_quantities.py

@@ -300,6 +300,16 @@ def __neg__(self) -> Self:
         negation._base_value = -self._base_value
         return negation
 
+    def __abs__(self) -> Self:
+        """Return the absolute value of this quantity.
+
+        Returns:
+            The absolute value of this quantity.
+        """
+        absolute = type(self).__new__(type(self))
+        absolute._base_value = abs(self._base_value)
+        return absolute
+
 
 class _NoDefaultConstructible(type):
     """A metaclass that disables the default constructor."""

tests/timeseries/test_quantities.py

@@ -350,3 +350,30 @@ def test_nan() -> None:
     assert f"{Energy.from_watt_hours(float('nan'))}" == "nan Wh"
     assert f"{Frequency.from_hertz(float('nan'))}" == "nan Hz"
     assert f"{Percentage.from_fraction(float('nan'))}" == "nan %"
+
+
+def test_abs() -> None:
+    """Test the absolute value of quantities."""
+    power = Power.from_watts(1000.0)
+    assert abs(power) == Power.from_watts(1000.0)
+    assert abs(-power) == Power.from_watts(1000.0)
+
+    voltage = Voltage.from_volts(230.0)
+    assert abs(voltage) == Voltage.from_volts(230.0)
+    assert abs(-voltage) == Voltage.from_volts(230.0)
+
+    current = Current.from_amperes(2)
+    assert abs(current) == Current.from_amperes(2)
+    assert abs(-current) == Current.from_amperes(2)
+
+    energy = Energy.from_kilowatt_hours(6.2)
+    assert abs(energy) == Energy.from_kilowatt_hours(6.2)
+    assert abs(-energy) == Energy.from_kilowatt_hours(6.2)
+
+    freq = Frequency.from_hertz(50)
+    assert abs(freq) == Frequency.from_hertz(50)
+    assert abs(-freq) == Frequency.from_hertz(50)
+
+    pct = Percentage.from_fraction(30)
+    assert abs(pct) == Percentage.from_fraction(30)
+    assert abs(-pct) == Percentage.from_fraction(30)