From a5b0bdf69547b638b7e03c5aa0273a34068eebe9 Mon Sep 17 00:00:00 2001
From: Ray Speth <speth@mit.edu>
Date: Sun, 18 Jun 2017 17:08:17 -0400
Subject: [PATCH] [Python] Make activity coefficients and activities accessible

---
 include/cantera/cython/wrappers.h             |  2 ++
 interfaces/cython/cantera/_cantera.pxd        |  2 ++
 interfaces/cython/cantera/test/test_thermo.py |  7 +++++++
 interfaces/cython/cantera/thermo.pyx          | 15 +++++++++++++++
 4 files changed, 26 insertions(+)

diff --git a/include/cantera/cython/wrappers.h b/include/cantera/cython/wrappers.h
index b4eb6508a..09aec98ef 100644
--- a/include/cantera/cython/wrappers.h
+++ b/include/cantera/cython/wrappers.h
@@ -85,6 +85,8 @@ THERMO_1D(getEntropy_R)
 THERMO_1D(getIntEnergy_RT)
 THERMO_1D(getGibbs_RT)
 THERMO_1D(getCp_R)
+THERMO_1D(getActivities)
+THERMO_1D(getActivityCoefficients)
 
 KIN_1D(getFwdRatesOfProgress)
 KIN_1D(getRevRatesOfProgress)
diff --git a/interfaces/cython/cantera/_cantera.pxd b/interfaces/cython/cantera/_cantera.pxd
index e6fd026e5..08e6165e8 100644
--- a/interfaces/cython/cantera/_cantera.pxd
+++ b/interfaces/cython/cantera/_cantera.pxd
@@ -823,6 +823,8 @@ cdef extern from "cantera/cython/wrappers.h":
     void thermo_getIntEnergy_RT(CxxThermoPhase*, double*) except +translate_exception
     void thermo_getGibbs_RT(CxxThermoPhase*, double*) except +translate_exception
     void thermo_getCp_R(CxxThermoPhase*, double*) except +translate_exception
+    void thermo_getActivities(CxxThermoPhase*, double*) except +translate_exception
+    void thermo_getActivityCoefficients(CxxThermoPhase*, double*) except +translate_exception
 
     # other ThermoPhase methods
     cdef void thermo_getMolecularWeights(CxxThermoPhase*, double*) except +translate_exception
diff --git a/interfaces/cython/cantera/test/test_thermo.py b/interfaces/cython/cantera/test/test_thermo.py
index 513cb663e..c27d04811 100644
--- a/interfaces/cython/cantera/test/test_thermo.py
+++ b/interfaces/cython/cantera/test/test_thermo.py
@@ -566,6 +566,13 @@ class TestThermoPhase(utilities.CanteraTest):
         cp = sum(self.phase.standard_cp_R * self.phase.X) * ct.gas_constant
         self.assertNear(cp, self.phase.cp_mole)
 
+    def test_activities(self):
+        self.phase.TDY = 850.0, 0.2, 'H2:0.1, H2O:0.6, AR:0.3'
+        self.assertArrayNear(self.phase.X, self.phase.activities)
+
+        self.assertArrayNear(self.phase.activity_coefficients,
+                             np.ones(self.phase.n_species))
+
     def test_isothermal_compressibility(self):
         self.assertNear(self.phase.isothermal_compressibility, 1.0/self.phase.P)
 
diff --git a/interfaces/cython/cantera/thermo.pyx b/interfaces/cython/cantera/thermo.pyx
index 4bbe40945..c95e43552 100644
--- a/interfaces/cython/cantera/thermo.pyx
+++ b/interfaces/cython/cantera/thermo.pyx
@@ -1216,6 +1216,21 @@ cdef class ThermoPhase(_SolutionBase):
         def __get__(self):
             return self._getArray1(thermo_getCp_R)
 
+    property activities:
+        """
+        Array of nondimensional activities. Returns either molar or molal
+        activities depending on the convention of the thermodynamic model.
+        """
+        def __get__(self):
+            return self._getArray1(thermo_getActivities)
+
+    property activity_coefficients:
+        """
+        Array of nondimensional, molar activity coefficients.
+        """
+        def __get__(self):
+            return self._getArray1(thermo_getActivityCoefficients)
+
     ######## Miscellaneous properties ########
     property isothermal_compressibility:
         """Isothermal compressibility [1/Pa]."""