Multipage App with session_state - Reload on pages sets st.session_state variables to NA

[FabK]

I have a multipage app, which is working ok, if I reload (F5) the app on the main page. But it does not reload the variables from st.session_state, if reloaded on another page (e.g. page1, page2). This behavior is of course not what a user wants. Therefore, the question: How to reload the entire app, if a user reloades on one of the other pages?

An example App:

.
├── home.py
└── pages
    └── page1.py

home.py

import streamlit as st

"# Home"

if "basename" not in st.session_state:
    st.session_state.basename = "a"

if "ext" not in st.session_state:
    st.session_state.ext = "txt"

if "file_name" not in st.session_state:
    st.session_state.file_name = ""

"#### Session state"
st.json(dict(sorted(st.session_state.items())))

page1.py

import streamlit as st

"#### Session state"
st.json(dict(sorted(st.session_state.items())))

"# Page1"

def get_file_name(basename, ext):
    return f"{basename}.{ext}"

if "basename" in st.session_state:
    basename = st.session_state.basename
else:
    basename = "NA"

basename = st.text_input("Basename", value=basename)
st.session_state.basename = basename

if "ext" in st.session_state:
    ext = st.session_state.ext
else:
    ext = "NA"

ext = st.text_input("Ext", value=ext)
st.session_state.ext = ext

st.session_state.file_name = get_file_name(st.session_state.basename, st.session_state.ext)

"#### Session state"
st.json(dict(sorted(st.session_state.items())))

[ferdy]

Whenever you define a session variable in the main page and this variable is used in other pages and user reloads a page that is not a main page, apply a switch_page()

Example:

page1.py

# page is reloaded
if "basename" not in st.session_state:
    st.switch_page('home.py')  # assuming basename is first defined in home.py

By switching to the main page, the original behavior of streamlit run is simulated that is streamlit starts at main page.

[FabK]

Thank you very much for your reply. I think, this is a viable workaround. I didn’t know about st.switch_page(), but hoped for this kind of fix.

I added this to page1.py and it does the job:

for v in ["basename", "ext", "file_name"]:
    if v not in st.session_state:
        st.switch_page('home.py')