I'm building a Streamlit app with multiple pages and need a global filter (like a dropdown) whose state persists across all pages. How should I structure this app, and what's the recommended way to implement the global filter so its state is maintained when users switch pages?
Navigate to the 'Multipage apps' section within the documentation. Review the 'Overview of multipage apps' to understand the main approaches. Identify the preferred method for structuring multipage apps for maximum flexibility. Navigate to the 'Working with widgets in multipage apps' section. Identify the preferred strategy for making a widget stateful across all pages. Formulate an answer that combines these two pieces of information, explaining the recommended approach and why it's preferred for global filter state persistence.
State that the preferred method for structuring the multipage app is using `st.Page` and `st.navigation`. Explain that when using `st.Page` and `st.navigation`, the entrypoint file acts as a 'picture frame' or 'router' for the pages. State that the preferred strategy for the global filter to persist its state across all pages is to define the widget (e.g., `st.selectbox`) in the entrypoint file. Mention that when a widget is defined in the entrypoint file, Streamlit associates its ID with the entrypoint, ensuring its state persists across page switches. Confirm that this approach does not work if the app is defined using the `pages/` directory method.