updated download button

app.py

@@ -48,12 +48,17 @@ if uploaded_file1 is not None and uploaded_file2 is not None:
 
     st.write(df1)
 
+    @st.cache
+    def convert_df_to_csv(df):
+      # IMPORTANT: Cache the conversion to prevent computation on every rerun
+      return df.to_csv().encode('utf-8')
+
+
     st.download_button(
-       "Press to Download",
-       df1,
-       "output_file.csv",
-       "text/csv",
-       key='download-csv'
+      label="Download data as CSV",
+      data=convert_df_to_csv(df1),
+      file_name='output.csv',
+      mime='text/csv',
     )