From 760679a8af634a7531a81d3671dd80517c6b540b Mon Sep 17 00:00:00 2001
From: Christian Hill <xn.hill@gmail.com>
Date: Wed, 27 Jul 2022 15:59:27 +0200
Subject: [PATCH] =?UTF-8?q?Silently=20change=20hv=20to=20h=CE=BD=20in=20?=
 =?UTF-8?q?=5Fparse=5Fformula=20and=20add=20a=20hash=20method?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 setup.py               |  2 +-
 src/pyvalem/formula.py | 18 ++++++++++++------
 tests/test_formula.py  | 10 ++++++++++
 3 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/setup.py b/setup.py
index a3cf6c8..e396ee5 100644
--- a/setup.py
+++ b/setup.py
@@ -8,7 +8,7 @@
 
 setup(
     name="pyvalem",
-    version="2.5.9",
+    version="2.5.10",
     description="A package for managing simple chemical species and states",
     long_description=long_description,
     long_description_content_type="text/x-rst",
diff --git a/src/pyvalem/formula.py b/src/pyvalem/formula.py
index 25eaed6..29cb50a 100644
--- a/src/pyvalem/formula.py
+++ b/src/pyvalem/formula.py
@@ -200,9 +200,10 @@ class Formula:
 
     Notes
     -----
-    The ``__repr__`` method is overloaded to provide a *canonicalised* representation
-    of the formula. The idea is that two formulas representing the same physical entity
-    will have the same ``repr(formula)`` representation.
+    The ``__repr__`` method is intended to be a *canonicalised* representation
+    of the formula, but no check is made to ensure that a single formula is used
+    to describe a unique species (e.g. "HD" and "DH" and "H(2H)" all have
+    different __repr__ representations.
 
     Examples
     --------
@@ -321,6 +322,10 @@ def _parse_formula(self, formula):
         if formula == "e":
             # Quietly convert e to e-.
             self.formula = formula = "e-"
+
+        if self.formula == "hv":
+            self.formula = "hν"
+
         if formula in special_cases:
             for attr, val in special_cases[formula].items():
                 setattr(self, attr, val)
@@ -506,12 +511,13 @@ def _get_charge_reps(charge):
         return "", "", ""
 
     def __repr__(self):
-        if self.formula == "hv":
-            return "hν"
         return self.formula
 
+    def __hash__(self):
+        return hash(self.formula)
+
     def __eq__(self, other):
-        return repr(self.formula) == repr(other.formula)
+        return self.formula == other.formula
 
     def _stoichiometric_formula_atomic_number(self):
         """Return a list of atoms/isotopes and their stoichiometries.
diff --git a/tests/test_formula.py b/tests/test_formula.py
index cb3950b..9fd1779 100644
--- a/tests/test_formula.py
+++ b/tests/test_formula.py
@@ -163,6 +163,16 @@ def test_parse_fail(self):
         self.assertRaises(FormulaParseError, Formula, "H3O^+")
         self.assertRaises(FormulaParseError, Formula, "H_2S")
 
+    def test_formula_hash(self):
+        f1 = Formula("hv")
+        f2 = Formula("Ar")
+        test_dict = {f1: 0, f2: "a"}
+        test_set = set((f1, f1, f2))
+
+        f3 = Formula("hν")
+        self.assertEqual(hash(f1), hash(f3))
+        self.assertEqual(repr(f1), repr(f3))
+
 
 if __name__ == "__main__":
     unittest.main()