Hello @e-tony, welcome to the forum!
Indeed, this is just a matter of logic. Are you expecting something like this? (I’ve removed pages)
from streamlit.hashing import _CodeHasher
from streamlit.report_thread import get_report_ctx
from streamlit.server.server import Server
from random import choices
from string import ascii_letters
import streamlit as st
DATES = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"]
def main():
state = _get_state()
st.write("**Current state:**", state.input)
predef = st.selectbox("Predefined input", options=DATES)
custom = st.text_input("Custom input")
random = "".join(choices(ascii_letters, k=10))
# This can be a function which changes state.input
if st.button("Random input"):
state.input = random
# Here we check if text input is empty or not
elif custom:
state.input = custom
# If we didn't call our function, and text input is empty, we use predefined choices
else:
state.input = predef
# Mandatory to avoid rollbacks with widgets, must be called at the end of your app
state.sync()
class _SessionState:
def __init__(self, session, hash_funcs):
"""Initialize SessionState instance."""
self.__dict__["_state"] = {
"data": {},
"hash": None,
"hasher": _CodeHasher(hash_funcs),
"is_rerun": False,
"session": session,
}
def __call__(self, **kwargs):
"""Initialize state data once."""
for item, value in kwargs.items():
if item not in self._state["data"]:
self._state["data"][item] = value
def __getitem__(self, item):
"""Return a saved state value, None if item is undefined."""
return self._state["data"].get(item, None)
def __getattr__(self, item):
"""Return a saved state value, None if item is undefined."""
return self._state["data"].get(item, None)
def __setitem__(self, item, value):
"""Set state value."""
self._state["data"][item] = value
def __setattr__(self, item, value):
"""Set state value."""
self._state["data"][item] = value
def clear(self):
"""Clear session state and request a rerun."""
self._state["data"].clear()
self._state["session"].request_rerun()
def sync(self):
"""Rerun the app with all state values up to date from the beginning to fix rollbacks."""
# Ensure to rerun only once to avoid infinite loops
# caused by a constantly changing state value at each run.
#
# Example: state.value += 1
if self._state["is_rerun"]:
self._state["is_rerun"] = False
elif self._state["hash"] is not None:
if self._state["hash"] != self._state["hasher"].to_bytes(self._state["data"], None):
self._state["is_rerun"] = True
self._state["session"].request_rerun()
self._state["hash"] = self._state["hasher"].to_bytes(self._state["data"], None)
def _get_session():
session_id = get_report_ctx().session_id
session_info = Server.get_current()._get_session_info(session_id)
if session_info is None:
raise RuntimeError("Couldn't get your Streamlit Session object.")
return session_info.session
def _get_state(hash_funcs=None):
session = _get_session()
if not hasattr(session, "_custom_session_state"):
session._custom_session_state = _SessionState(session, hash_funcs)
return session._custom_session_state
if __name__ == "__main__":
main()