Make orbital tab optional when Psikit unavailable

app.py

@@ -87,25 +87,32 @@ def smiles_to_name(smiles: str) -> str:
 
 
 def smiles_to_molecular_orbitals(smiles: str) -> str:
-    """Generate HOMO/LUMO isosurfaces using Psikit and render with py3Dmol."""
+    """Generate HOMO/LUMO isosurfaces using Psikit, when available."""
     mol = _mol_from_smiles(smiles)
     if mol.GetNumAtoms() > 30:
         raise gr.Error("Please provide a molecule with 30 atoms or fewer for orbital visualization.")
 
     try:
-        from psikit import Psikit
-    except ImportError as exc:  # pragma: no cover - runtime dependency
-        raise gr.Error("Psikit is required for molecular orbital visualization.") from exc
+        from psikit import Psikit  # type: ignore[import]
+    except ImportError:
+        return (
+            "<p><strong>Molecular orbital rendering requires Psikit + Psi4.</strong> "
+            "Install them locally with <code>pip install psikit psi4 py3Dmol</code> "
+            "and run this app on your machine.</p>"
+        )
 
     try:
-        import py3Dmol
-    except ImportError as exc:  # pragma: no cover - runtime dependency
-        raise gr.Error("py3Dmol is required for molecular orbital visualization.") from exc
+        import py3Dmol  # type: ignore[import]
+    except ImportError:
+        return (
+            "<p><strong>py3Dmol is missing.</strong> Install it with <code>pip install py3Dmol</code> "
+            "to view orbital isosurfaces.</p>"
+        )
 
     with tempfile.TemporaryDirectory() as tmpdir:
         original_cwd = os.getcwd()
+        os.chdir(tmpdir)
         try:
-            os.chdir(tmpdir)
             pk = Psikit()
             pk.read_from_smiles(smiles)
             pk.optimize()
@@ -113,36 +120,43 @@ def smiles_to_molecular_orbitals(smiles: str) -> str:
 
             cube_candidates = sorted(Path(tmpdir).glob("Psi_a_*A.cube"))
             if not cube_candidates:
-                raise gr.Error("Failed to generate molecular orbital cube files. Try a smaller molecule.")
+                return (
+                    "<p>Psikit did not produce cube files. Try a smaller molecule or different conformer.</p>"
+                )
 
             mol_block = Chem.MolToMolBlock(pk.mol)
-        except Exception as exc:
-            raise gr.Error(f"Unable to compute molecular orbitals: {exc}") from exc
+
+            html_sections: list[str] = []
+            labels = ["HOMO", "LUMO"]
+            for cube_file, label in zip(cube_candidates[:2], labels):
+                cube_data = cube_file.read_text()
+                view = py3Dmol.view(width=500, height=400)
+                view.addModel(mol_block, "mol")
+                view.setStyle({"stick": {}})
+                isoval = 0.02
+                # Use the same volumetric data for positive/negative isosurfaces.
+                view.addVolumetricData(
+                    cube_data,
+                    "cube",
+                    {"isoval": isoval, "color": "blue", "opacity": 0.6},
+                )
+                view.addVolumetricData(
+                    cube_data,
+                    "cube",
+                    {"isoval": -isoval, "color": "red", "opacity": 0.6},
+                )
+                view.zoomTo()
+                html_sections.append(f"<h3>{label}</h3>" + view._make_html())
+
+            if not html_sections:
+                return "<p>Could not prepare HOMO/LUMO visualizations.</p>"
+
+            return "".join(html_sections)
+        except Exception as exc:  # pragma: no cover - runtime heavy
+            return f"<p>Unable to compute molecular orbitals: {exc}</p>"
         finally:
             os.chdir(original_cwd)
 
-    def _render_cube(cube_path: Path, title: str) -> str:
-        cube_data = cube_path.read_text()
-        view = py3Dmol.view(width=500, height=400)
-        view.addModel(mol_block, "mol")
-        view.setStyle({"stick": {}})
-        isoval = 0.02
-        view.addVolumetricData(cube_data, "cube", {"isoval": isoval, "color": "blue", "opacity": 0.6})
-        view.addVolumetricData(cube_data, "cube", {"isoval": -isoval, "color": "red", "opacity": 0.6})
-        view.zoomTo()
-        return f"<h3>{title}</h3>" + view._make_html()
-
-    # First cube is HOMO, second is LUMO following psikit naming convention.
-    html_sections = []
-    labels = ["HOMO", "LUMO"]
-    for cube_file, label in zip(cube_candidates[:2], labels):
-        html_sections.append(_render_cube(cube_file, label))
-
-    if not html_sections:
-        raise gr.Error("Could not prepare HOMO/LUMO visualizations.")
-
-    return "".join(html_sections)
-
 
 def name_to_3d_molecule(name: str) -> str:
     """Convert chemical name to 3D molecule visualization"""

requirements.txt

@@ -3,7 +3,4 @@ rdkit
 gradio==4.44.1
 huggingface_hub==0.19.4
 cirpy
-pubchempy
-psikit
-psi4
-py3Dmol
+pubchempy