[Python] Interface.coverages can be set using a string or dict

interfaces/cython/cantera/_cantera.pxd

@@ -213,6 +213,7 @@ cdef extern from "cantera/thermo/SurfPhase.h":
         double siteDensity()
         void setSiteDensity(double)
         void setCoverages(double*) except +
+        void setCoveragesByName(Composition&) except +
         void getCoverages(double*) except +
 
 

interfaces/cython/cantera/test/test_thermo.py

@@ -557,6 +557,31 @@ class TestInterfacePhase(utilities.CanteraTest):
         self.interface.site_density = 100
         self.assertNear(self.interface.site_density, 100)
 
+    def test_coverages_array(self):
+        C = np.zeros(self.interface.n_species)
+        C[1] = 0.25
+        C[3] = 0.125
+        C[4] = 0.125
+        self.interface.coverages = C
+        C = self.interface.coverages
+        # should now be normalized
+        self.assertNear(C[1], 0.5)
+        self.assertNear(C[3], 0.25)
+        self.assertNear(C[4], 0.25)
+        self.assertNear(sum(C), 1.0)
+
+    def test_coverages_string(self):
+        self.interface.coverages = 'c6HM:0.2, c6H*:0.8'
+        C = self.interface.coverages
+        self.assertNear(C[self.interface.species_index('c6HM')], 0.2)
+        self.assertNear(C[self.interface.species_index('c6H*')], 0.8)
+
+    def test_coverages_dict(self):
+        self.interface.coverages = {'c6**':1.0, 'c6*M':3.0}
+        C = self.interface.coverages
+        self.assertNear(C[self.interface.species_index('c6**')], 0.25)
+        self.assertNear(C[self.interface.species_index('c6*M')], 0.75)
+
 
 class ImportTest(utilities.CanteraTest):
     """

interfaces/cython/cantera/thermo.pyx

@@ -1067,6 +1067,10 @@ cdef class InterfacePhase(ThermoPhase):
                 return data
 
         def __set__(self, theta):
+            if isinstance(theta, (dict, str, unicode, bytes)):
+                self.surf.setCoveragesByName(comp_map(theta))
+                return
+
             if len(theta) != self.n_species:
                 raise ValueError("Array has incorrect length")
             cdef np.ndarray[np.double_t, ndim=1] data = \