Update app.py

app.py

@@ -33,10 +33,9 @@ def run_hardy_cross(file, loops_json, max_iterations, tolerance):
             plot_path
         )
     except Exception as e:
-        # Full traceback for clear debugging in output
-        error_message = f"❌ **Error:** {str(e)}\n\n```
-{traceback.format_exc()}
-```"
+        # Full traceback for clear debugging in output (corrected syntax)
+        tb = traceback.format_exc()
+        error_message = f"❌ **Error:** {str(e)}\n\n```\n{tb}\n```"
         return error_message, "", ""
 
 demo = gr.Interface(