Update src/streamlit_app.py

src/streamlit_app.py

@@ -13,6 +13,10 @@ st.set_page_config(layout="wide", page_title="Multiplex Coop Housing Filter")
 st.title("🗺️ Multiplex Coop Housing Filter (Hugging Face Data)")
 st.write("This app uses the `ProjectMultiplexCoop/PropertyBoundaries` dataset from Hugging Face. Draw a polygon on the map to spatially filter properties. Use the form below to apply additional filters based on property attributes. **Note: FSI, Building Coverage, Height, and Stories are synthetic for demonstration as they are not directly available in the dataset.**")
 
+# --- Configuration Constants ---
+MAX_ROWS_DATAFRAME_DISPLAY = 1000  # Max rows to show in st.dataframe
+MAX_MAP_FEATURES_DISPLAY = 5000    # Max features to plot on the Folium map to prevent MessageSizeError
+
 # --- 1. Load Data from Hugging Face and Process ---
 @st.cache_data
 def load_and_process_data():
@@ -202,8 +206,7 @@ with st.form("attribute_filters"):
         st.info("Adjust filters and click 'Apply Attribute Filters'.")
 
 
-# --- 4. Display Filtered Data on a New Map and as a Table (now in an expander) ---
-# The expander is expanded by default to show results immediately after filtering
+# --- 4. Display Filtered Data on a New Map and as a Table ---
 with st.expander("Filtered Properties Display", expanded=True):
     if not filtered_df.empty:
         # Calculate bounds for filtered data to set appropriate zoom
@@ -235,12 +238,20 @@ with st.expander("Filtered Properties Display", expanded=True):
                 fill_opacity=0.5
             ).add_to(filtered_m)
 
-        # Convert filtered_df back to GeoDataFrame for direct plotting of geometries
+        # Convert filtered_df to GeoDataFrame for plotting
         filtered_gdf = gpd.GeoDataFrame(filtered_df, geometry='geometry')
 
+        # --- Apply map display limit ---
+        features_to_plot_count = len(filtered_gdf)
+        if features_to_plot_count > MAX_MAP_FEATURES_DISPLAY:
+            st.warning(f"Displaying a random sample of {MAX_MAP_FEATURES_DISPLAY} properties on the map (out of {features_to_plot_count} total filtered) to prevent performance issues.")
+            filtered_gdf_for_map = filtered_gdf.sample(MAX_MAP_FEATURES_DISPLAY, random_state=42)
+        else:
+            filtered_gdf_for_map = filtered_gdf
+
         # Add filtered polygons to the map as GeoJSON layer
         folium.GeoJson(
-            filtered_gdf.to_json(),
+            filtered_gdf_for_map.to_json(),
             style_function=lambda x: {
                 'fillColor': 'green',
                 'color': 'darkgreen',
@@ -257,13 +268,11 @@ with st.expander("Filtered Properties Display", expanded=True):
         st_folium(filtered_m, width=1000, height=500)
 
         st.subheader("Filtered Properties Table")
-        # Limit rows displayed in the dataframe to prevent MessageSizeError
-        MAX_ROWS_DISPLAY = 1000 # Define a reasonable limit
         display_cols = ['PARCELID', 'zn_type', 'zn_area', 'fsi_total', 'prcnt_cver', 'height_metres', 'stories', 'ADDRESS_NUMBER', 'LINEAR_NAME_FULL']
 
-        if len(filtered_df) > MAX_ROWS_DISPLAY:
-            st.warning(f"Displaying only the first {MAX_ROWS_DISPLAY} rows of the filtered data ({len(filtered_df)} total properties). Download the full dataset below.")
-            st.dataframe(filtered_df[display_cols].head(MAX_ROWS_DISPLAY))
+        if len(filtered_df) > MAX_ROWS_DATAFRAME_DISPLAY:
+            st.warning(f"Displaying only the first {MAX_ROWS_DATAFRAME_DISPLAY} rows of the filtered data ({len(filtered_df)} total properties). Download the full dataset below.")
+            st.dataframe(filtered_df[display_cols].head(MAX_ROWS_DATAFRAME_DISPLAY))
         else:
             st.dataframe(filtered_df[display_cols])
 
@@ -284,10 +293,12 @@ st.markdown("---")
 st.markdown(
     """
     **Troubleshooting Large Data:**
-    If you encounter a `MessageSizeError` when displaying a large number of filtered properties,
-    it means the data size exceeds Streamlit's default limit.
-    You can increase this limit by adding `server.maxMessageSize = <size_in_mb>`
-    (e.g., `server.maxMessageSize = 500`) to your Streamlit `config.toml` file.
+    If you still encounter a `MessageSizeError` despite the display limits,
+    it means the data size still exceeds Streamlit's internal limit, or the sampled data is still too complex.
+    You can try decreasing `MAX_MAP_FEATURES_DISPLAY` and `MAX_ROWS_DATAFRAME_DISPLAY` further.
+    Alternatively, you can increase Streamlit's default message size limit by adding
+    `server.maxMessageSize = <size_in_mb>` (e.g., `server.maxMessageSize = 500`)
+    to your Streamlit `config.toml` file.
     However, be aware that increasing this limit can lead to longer loading times and higher
     memory consumption in your browser and on the Streamlit server.
     """