Update app.py

app.py

@@ -48,8 +48,8 @@ if df1_upload is not None and df2_upload is not None:
     if not df1.empty and not df2.empty:
         columns_df1 = df1.columns.tolist()
         columns_df2 = df2.columns.tolist()
-        selected_columns_df1 = st.multiselect("Select columns from DataFrame 1 to match on:", columns_df1, default=columns_df1[0])
-        selected_columns_df2 = st.multiselect("Select columns from DataFrame 2 to match on:", columns_df2, default=columns_df2[0])
+        selected_columns_df1 = list(st.multiselect("Select columns from DataFrame 1 to match on:", columns_df1, default=columns_df1[0]))
+        selected_columns_df2 = list(st.multiselect("Select columns from DataFrame 2 to match on:", columns_df2, default=columns_df2[0]))
         st.write(selected_columns_df1)
         st.write(selected_columns_df2)