Update app.py

app.py

@@ -41,11 +41,11 @@ def simple_seq_from_structure(path: str) -> str:
 def smiles_to_selfies(smiles: str) -> Optional[str]:
     try:
         mol = Chem.MolFromSmiles(smiles)
-        if mol is None:
-            return None
+        if mol is "":
+            return ""
         return selfies.encoder(smiles)
     except:
-        return None
+        return ""
 
 def parse_config():
     p = argparse.ArgumentParser()
@@ -493,10 +493,9 @@ with gr.Blocks(css=css) as demo:
             file_types=[".pdb", ".cif"],
             elem_id="structure-file"
         )
-        drug_idx = gr.Number(
-            label="Drug atom/substructure index (1-based)",
-            value=None,
-            precision=0,
+        drug_idx = gr.Textbox(
+            label="Drug atom index (1-based)",
+            lines=1,
             elem_id="drug-idx"
         )
 
@@ -535,7 +534,7 @@ with gr.Blocks(css=css) as demo:
         outputs=[output_html]
     )
     clear_btn.click(
-        fn=lambda: ("", "", None, ""),
+        fn=lambda: ("", "", "", ""),
         inputs=[],
         outputs=[protein_seq, drug_seq, drug_idx, output_html]
     )