Stateful Streamlit data editory

home.py

#Put home.py in a working directory. Put page_1.py and page_2.py in a folder named pages.

import streamlit as st
import pandas as pd

def initialize():
    # the data
    st.session_state.df1 = pd.DataFrame({'A':[1,2],'B':[3,4]})
    st.session_state.df2 = pd.DataFrame({'A':[1,2],'B':[3,4]})
    # the shadow data
    st.session_state._df1 = pd.DataFrame({'A':[1,2],'B':[3,4]})
    st.session_state._df2 = pd.DataFrame({'A':[1,2],'B':[3,4]})

def changed_page(page):
    'Detect if the page was changed'
    if st.session_state.get('page') == page:
        return False
    st.session_state.page = page # initialize or change
    return True

def save(df_name):
    'Overwrite data with shadow data'
    st.session_state[df_name] = st.session_state['_'+df_name]

if 'df1' not in st.session_state:
    initialize()

if changed_page('home'):
    save('df1')
    save('df2')

st.header('df1')
st.write(st.session_state.df1)
st.header('df2')
st.write(st.session_state.df2)

page_1.py

import streamlit as st
import pandas as pd
from home import initialize, changed_page, save

if 'df1' not in st.session_state:
    initialize()

if changed_page('page1'):
    save('df1')
    save('df2')

st.session_state._df1 = st.data_editor(st.session_state.df1)

page_2.py

import streamlit as st
import pandas as pd
from home import initialize, changed_page, save

if 'df1' not in st.session_state:
    initialize()

if changed_page('page2'):
    save('df1')
    save('df2')

st.session_state._df2 = st.data_editor(st.session_state.df2)