jeremyjordan · July 1, 2025 22:20 · Oct 2, 2019 · Oct 2, 2019
diff --git a/pages.py b/pages.py
@@ -1,72 +1,7 @@
 import numpy as np
 import streamlit as st
-import streamlit.ReportThread as ReportThread
-from streamlit.server.Server import Server
-
-
-class SessionState(object):
-    def __init__(self, **kwargs):
-        """A new SessionState object.
-        Parameters
-        ----------
-        **kwargs : any
-            Default values for the session state.
-        Example
-        -------
-        >>> session_state = SessionState(user_name='', favorite_color='black')
-        >>> session_state.user_name = 'Mary'
-        ''
-        >>> session_state.favorite_color
-        'black'
-        """
-        for key, val in kwargs.items():
-            setattr(self, key, val)
-
-    def get(**kwargs):
-        """Gets a SessionState object for the current session.
-        Creates a new object if necessary.
-        Parameters
-        ----------
-        **kwargs : any
-            Default values you want to add to the session state, if we're creating a
-            new one.
-        Example
-        -------
-        >>> session_state = get(user_name='', favorite_color='black')
-        >>> session_state.user_name
-        ''
-        >>> session_state.user_name = 'Mary'
-        >>> session_state.favorite_color
-        'black'
-        Since you set user_name above, next time your script runs this will be the
-        result:
-        >>> session_state = get(user_name='', favorite_color='black')
-        >>> session_state.user_name
-        'Mary'
-        """
-        # Hack to get the session object from Streamlit.
-
-        ctx = ReportThread.get_report_ctx()
-
-        session = None
-        session_infos = Server.get_current()._session_infos.values()
-
-        for session_info in session_infos:
-            if session_info.session._main_dg == ctx.main_dg:
-                session = session_info.session
-
-        if session is None:
-            raise RuntimeError(
-                "Oh noes. Couldn't get your Streamlit Session object"
-                'Are you doing something fancy with threads?')
-
-        # Got the session object! Now let's attach some state into it.
-
-        if not getattr(session, '_custom_session_state', None):
-            session._custom_session_state = SessionState(**kwargs)
-
-        return session._custom_session_state
 
+from .streamlit_utils import SessionState
 
 session_state = SessionState.get(page=1)
 

diff --git a/streamlit_utils.py b/streamlit_utils.py
@@ -0,0 +1,70 @@
+'''
+An example implementation from https://discuss.streamlit.io/t/preserving-state-across-sidebar-pages/107
+'''
+
+import streamlit.ReportThread as ReportThread
+from streamlit.server.Server import Server
+
+
+class SessionState(object):
+    def __init__(self, **kwargs):
+        """A new SessionState object.
+        Parameters
+        ----------
+        **kwargs : any
+            Default values for the session state.
+        Example
+        -------
+        >>> session_state = SessionState(user_name='', favorite_color='black')
+        >>> session_state.user_name = 'Mary'
+        ''
+        >>> session_state.favorite_color
+        'black'
+        """
+        for key, val in kwargs.items():
+            setattr(self, key, val)
+
+    def get(**kwargs):
+        """Gets a SessionState object for the current session.
+        Creates a new object if necessary.
+        Parameters
+        ----------
+        **kwargs : any
+            Default values you want to add to the session state, if we're creating a
+            new one.
+        Example
+        -------
+        >>> session_state = get(user_name='', favorite_color='black')
+        >>> session_state.user_name
+        ''
+        >>> session_state.user_name = 'Mary'
+        >>> session_state.favorite_color
+        'black'
+        Since you set user_name above, next time your script runs this will be the
+        result:
+        >>> session_state = get(user_name='', favorite_color='black')
+        >>> session_state.user_name
+        'Mary'
+        """
+        # Hack to get the session object from Streamlit.
+
+        ctx = ReportThread.get_report_ctx()
+
+        session = None
+        session_infos = Server.get_current()._session_infos.values()
+
+        for session_info in session_infos:
+            if session_info.session._main_dg == ctx.main_dg:
+                session = session_info.session
+
+        if session is None:
+            raise RuntimeError(
+                "Oh noes. Couldn't get your Streamlit Session object"
+                'Are you doing something fancy with threads?')
+
+        # Got the session object! Now let's attach some state into it.
+
+        if not getattr(session, '_custom_session_state', None):
+            session._custom_session_state = SessionState(**kwargs)
+
+        return session._custom_session_state
diff --git a/pages.py b/pages.py
@@ -0,0 +1,123 @@
+import numpy as np
+import streamlit as st
+import streamlit.ReportThread as ReportThread
+from streamlit.server.Server import Server
+
+
+class SessionState(object):
+    def __init__(self, **kwargs):
+        """A new SessionState object.
+        Parameters
+        ----------
+        **kwargs : any
+            Default values for the session state.
+        Example
+        -------
+        >>> session_state = SessionState(user_name='', favorite_color='black')
+        >>> session_state.user_name = 'Mary'
+        ''
+        >>> session_state.favorite_color
+        'black'
+        """
+        for key, val in kwargs.items():
+            setattr(self, key, val)
+
+    def get(**kwargs):
+        """Gets a SessionState object for the current session.
+        Creates a new object if necessary.
+        Parameters
+        ----------
+        **kwargs : any
+            Default values you want to add to the session state, if we're creating a
+            new one.
+        Example
+        -------
+        >>> session_state = get(user_name='', favorite_color='black')
+        >>> session_state.user_name
+        ''
+        >>> session_state.user_name = 'Mary'
+        >>> session_state.favorite_color
+        'black'
+        Since you set user_name above, next time your script runs this will be the
+        result:
+        >>> session_state = get(user_name='', favorite_color='black')
+        >>> session_state.user_name
+        'Mary'
+        """
+        # Hack to get the session object from Streamlit.
+
+        ctx = ReportThread.get_report_ctx()
+
+        session = None
+        session_infos = Server.get_current()._session_infos.values()
+
+        for session_info in session_infos:
+            if session_info.session._main_dg == ctx.main_dg:
+                session = session_info.session
+
+        if session is None:
+            raise RuntimeError(
+                "Oh noes. Couldn't get your Streamlit Session object"
+                'Are you doing something fancy with threads?')
+
+        # Got the session object! Now let's attach some state into it.
+
+        if not getattr(session, '_custom_session_state', None):
+            session._custom_session_state = SessionState(**kwargs)
+
+        return session._custom_session_state
+
+
+session_state = SessionState.get(page=1)
+
+
+def main():
+    # Render the readme as markdown using st.markdown.
+    readme_text = st.markdown('''
+    # Instructions
+
+    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed vel lorem tincidunt, 
+    congue orci id, pretium augue. Curabitur facilisis malesuada justo. Sed tincidunt 
+    metus sed arcu blandit efficitur. Vestibulum ut neque sed diam dapibus imperdiet 
+    id sit amet ante. In in sollicitudin est, ut bibendum lectus. Curabitur posuere 
+    cursus dui. Nullam interdum eu nunc ac bibendum. Etiam id dolor laoreet nulla euismod 
+    tristique. Nulla mollis condimentum auctor. Mauris ut diam ante. Maecenas at mauris 
+    vulputate, hendrerit erat in, viverra libero. Nulla viverra lacus vitae urna hendrerit 
+    fringilla. Aliquam pharetra justo vitae neque semper, a consequat lorem varius.
+    ''')
+
+    # Add a selector for the app mode on the sidebar.
+    st.sidebar.title("What to do")
+    app_mode = st.sidebar.selectbox(
+        "Choose the app mode",
+        ["Instructions", "Show paginated content"]
+    )
+    if app_mode == "Instructions":
+        st.sidebar.success('To continue select an option in the dropdown menu.')
+    elif app_mode == "Show paginated content":
+        readme_text.empty()
+        prev_page = st.button('prev')
+        if prev_page:
+            session_state.page -= 1
+        next_page = st.button('next')
+        if next_page:
+            session_state.page += 1
+        st.write(f'page: {session_state.page}')
+        load_data(page=session_state.page)
+
+
+def load_data(page=1):
+    data = np.arange(1, 100)
+    page = max(page, 1)
+    per_page = 10
+    start = (page - 1) * per_page
+    end = page * per_page
+    results = data[start:end]
+
+    for i in results:
+        st.subheader(i)
+        st.text('Lorem ipsum dolor sit amet, consectetur adipiscing elit.')
+
+
+if __name__ == "__main__":
+    main()