Add PubChem fallback for SMILES name lookup

app.py

@@ -2,6 +2,7 @@ import gradio as gr
 from rdkit import Chem
 from rdkit.Chem import Descriptors, Draw, AllChem
 import cirpy
+import pubchempy as pcp
 from urllib.error import HTTPError, URLError
 
 
@@ -54,19 +55,32 @@ def name_to_smiles(name: str) -> str:
 def smiles_to_name(smiles: str) -> str:
     """Convert SMILES string to chemical name using Chemical Identifier Resolver (CIR)."""
     mol = _mol_from_smiles(smiles)
+    canonical_smiles = Chem.MolToSmiles(mol)
 
     try:
         name = cirpy.resolve(smiles, "name")
-    except (HTTPError, URLError) as network_error:
-        # Gracefully degrade when the resolver service is unavailable.
-        return f"Resolver unavailable ({network_error}). Canonical SMILES: {Chem.MolToSmiles(mol)}"
-    except Exception as e:
-        return f"Unable to resolve to name ({e}). Canonical SMILES: {Chem.MolToSmiles(mol)}"
-
-    if not name:
-        return f"No name found. Canonical SMILES: {Chem.MolToSmiles(mol)}"
+        if name:
+            return name
+    except (HTTPError, URLError):
+        # Ignore network failures and fall back to other resolvers.
+        pass
+    except Exception:
+        # Ignore unexpected CIR errors and fall back to other resolvers.
+        pass
 
-    return name
+    try:
+        # Try PubChem as a secondary resolver in case CIR fails.
+        compounds = pcp.get_compounds(canonical_smiles, namespace="smiles")
+        for compound in compounds:
+            if compound.iupac_name:
+                return compound.iupac_name
+            if compound.synonyms:
+                return compound.synonyms[0]
+    except Exception:
+        # Ignore PubChem issues and fall back to canonical SMILES output.
+        pass
+
+    return f"No name available. Canonical SMILES: {canonical_smiles}"
 
 
 def name_to_3d_molecule(name: str) -> str:

requirements.txt

@@ -2,4 +2,5 @@
 rdkit
 gradio==4.44.1
 huggingface_hub==0.19.4
-cirpy
+cirpy
+pubchempy