Update app.py

app.py

@@ -43,7 +43,7 @@ SYSTEM_INSTRUCTION = (
     "2. **Code:** If the question requires calculation, aggregation, or visualization, you MUST generate Python code to execute against the 'df' DataFrame. "
     "   - The DataFrame is already loaded as a variable named 'df'. Do NOT redefine it. "
     "   - Use Streamlit functions for simple outputs: `st.dataframe(...)`, `st.bar_chart()`, `st.line_chart()`. "
-    "   - For custom, complex plots, you MUST use Matplotlib: start with `plt.figure()`, then use `plt.` commands (like `plt.hist()`), and finish with `st.pyplot(plt)` to display the plot. "
+    "   - For **ALL** custom, complex plots, you MUST follow this strict Matplotlib sequence: **Start with `plt.figure()`, use `plt.` commands for plotting, and explicitly end with `st.pyplot(plt)`** to display the output. "
     "   - Ensure the code is self-contained and ready to execute."
 )
 
@@ -162,8 +162,12 @@ if uploaded:
                             'np': np,
                             'plt': plt, # Explicitly include pyplot here
                         }
+                        
+                        # Append a neutral statement to the code to prevent implicit Streamlit display of the last value
+                        final_code = code + "\nNone" 
+                        
                         # Executing the code within the local scope
-                        exec(code, globals(), local_scope)
+                        exec(final_code, globals(), local_scope)
                         
                         # FIX: Explicitly close all Matplotlib figures to prevent cross-run contamination
                         plt.close('all')