Merge pull request #226 from DNIIBOY/hashed-substance

Add __hash__ method to Substance class

chempy/chemistry.py

@@ -98,6 +98,16 @@ def __eq__(self, other):
                 return False
         return True
 
+    def __hash__(self) -> int:
+        hashed_values = []
+        for key in self.attrs:
+            value = getattr(self, key)
+            if isinstance(value, dict):
+                hashed_values.append(hash(tuple(sorted(value.items()))))
+            else:
+                hashed_values.append(hash(value))
+        return sum(hashed_values)
+
     @property
     def charge(self):
         """Convenience property for accessing ``composition[0]``"""

chempy/tests/test_chemistry.py

@@ -40,6 +40,8 @@ def test_Substance():
     assert s.composition == {0: 1, 1: 1}
     assert s.charge == 1
     assert abs(s.mass - 1.008) < 1e-3
+    assert s in {s: 1}
+    assert hash(s) != hash(Substance.from_formula("He"))
 
 
 def test_Substance__2():