Add class for representing Current quantities

Signed-off-by: Sahas Subramanian <[email protected]>

Author: shsms

src/frequenz/sdk/timeseries/_quantities.py

@@ -352,3 +352,53 @@ def as_megawatts(self) -> float:
             The power in megawatts.
         """
         return self._base_value / 1e6
+
+
+class Current(
+    Quantity,
+    exponent_unit_map={
+        -3: "mA",
+        0: "A",
+    },
+):
+    """A current quantity."""
+
+    @classmethod
+    def from_amperes(cls, amperes: float) -> Self:
+        """Initialize a new current quantity.
+
+        Args:
+            amperes: The current in amperes.
+
+        Returns:
+            A new current quantity.
+        """
+        return cls(value=amperes, exponent=0)
+
+    @classmethod
+    def from_milliamperes(cls, milliamperes: float) -> Self:
+        """Initialize a new current quantity.
+
+        Args:
+            milliamperes: The current in milliamperes.
+
+        Returns:
+            A new current quantity.
+        """
+        return cls(value=milliamperes, exponent=-3)
+
+    def as_amperes(self) -> float:
+        """Return the current in amperes.
+
+        Returns:
+            The current in amperes.
+        """
+        return self._base_value
+
+    def as_milliamperes(self) -> float:
+        """Return the current in milliamperes.
+
+        Returns:
+            The current in milliamperes.
+        """
+        return self._base_value * 1e3

tests/timeseries/test_quantities.py

@@ -5,7 +5,7 @@
 
 import pytest
 
-from frequenz.sdk.timeseries._quantities import Power, Quantity
+from frequenz.sdk.timeseries._quantities import Current, Power, Quantity
 
 
 class Fz1(
@@ -161,3 +161,18 @@ def test_power() -> None:
     assert power == Power.from_milliwatts(1200000.0)
     assert power == Power.from_megawatts(0.0012)
     assert power != Power.from_watts(1000.0)
+
+
+def test_current() -> None:
+    """Test the current class."""
+    current = Current.from_milliamperes(0.0000002)
+    assert f"{current:.9}" == "0.0000002 mA"
+    current = Current.from_amperes(600000.0)
+    assert f"{current}" == "600000 A"
+
+    current = Current.from_amperes(6.0)
+    assert current.as_amperes() == 6.0
+    assert current.as_milliamperes() == 6000.0
+    assert current == Current.from_milliamperes(6000.0)
+    assert current == Current.from_amperes(6.0)
+    assert current != Current.from_amperes(5.0)