Merge pull request #52 from portyanikhin/with-state-specified-phase

The `with_state` method of the `Fluid` and `Mixture` classes no longer resets the specified phase

Author: portyanikhin

pyfluids/fluids/abstract_fluid.py

@@ -45,6 +45,7 @@ def __init__(self):
         self.__temperature: float | None = None
         self.__triple_pressure: float | None = None
         self.__triple_temperature: float | None = None
+        self.__specified_phase: Phases | None = None
         self._unit_converter: UnitConverter = UnitConverter()
         self._fraction_unit: str = (
             " %" if self.units_system == UnitsSystem.SIWithCelsiusAndPercents else ""
@@ -321,6 +322,8 @@ def with_state(self, first_input: Input, second_input: Input) -> AbstractFluid:
         :raises ValueError: If input is invalid.
         """
         fluid = self.factory()
+        if self.__specified_phase is not None:
+            fluid.specify_phase(self.__specified_phase)
         fluid.update(first_input, second_input)
         return fluid
 
@@ -373,6 +376,7 @@ def specify_phase(self, phase: Phases) -> AbstractFluid:
         :return: Current fluid instance.
         """
         self._backend.specify_phase(phase.value)
+        self.__specified_phase = phase
         return self
 
     def unspecify_phase(self) -> AbstractFluid:
@@ -382,6 +386,7 @@ def unspecify_phase(self) -> AbstractFluid:
         :return: Current fluid instance.
         """
         self._backend.unspecify_phase()
+        self.__specified_phase = None
         return self
 
     def isentropic_compression_to_pressure(self, pressure: float) -> AbstractFluid:

tests/fluids/test_fluid.py

@@ -152,9 +152,11 @@ def test_update_various_fluids_matches_with_coolprop(self, name: FluidsList):
         )
         assert all(
             [
-                True
-                if actual[i] is None and expected[i] is None
-                else abs(actual[i] - expected[i]) < 1e-9
+                (
+                    True
+                    if actual[i] is None and expected[i] is None
+                    else abs(actual[i] - expected[i]) < 1e-9
+                )
                 for i in range(len(actual))
             ]
         )
@@ -170,10 +172,34 @@ def test_specify_phase_always_specifies_phase_for_all_further_calculations(self)
         self.fluid.specify_phase(Phases.Gas)
         with pytest.raises(ValueError):
             self.fluid.update(Input.pressure(101325), Input.temperature(20))
+        with pytest.raises(ValueError):
+            self.fluid.with_state(Input.pressure(101325), Input.temperature(20))
         self.fluid.unspecify_phase()
         self.fluid.update(
             Input.pressure(101325), Input.temperature(20)
         )  # does not raise
+        self.fluid.with_state(
+            Input.pressure(101325), Input.temperature(20)
+        )  # does not raise
+
+    def test_specify_phase_always_with_methods_chaining_works_same_way(self):
+        with pytest.raises(ValueError):
+            self.fluid.specify_phase(Phases.Gas).update(
+                Input.pressure(101325), Input.temperature(20)
+            )
+        self.fluid.unspecify_phase()
+        with pytest.raises(ValueError):
+            self.fluid.specify_phase(Phases.Gas).with_state(
+                Input.pressure(101325), Input.temperature(20)
+            )
+        self.fluid.specify_phase(Phases.Gas)
+        self.fluid.unspecify_phase().update(
+            Input.pressure(101325), Input.temperature(20)
+        )  # does not raise
+        self.fluid.specify_phase(Phases.Gas)
+        self.fluid.unspecify_phase().with_state(
+            Input.pressure(101325), Input.temperature(20)
+        )  # does not raise
 
     def test_equals_same_returns_true(self):
         origin = self.fluid.with_state(Input.pressure(101325), Input.temperature(5))