Prevent default value of multiselect from being deleted?

🎈 Using Streamlit
1

Hello,

I have a multiselect with a single default option, because it is required for the app to work. I wrote a callback to capture when the user deleted the default and warned them that it would be added back to the selected list. However, this does not work.

st.multiselect("RANK BY",
                    key="q_rank_by",
                    default=st.session_state["q_rank_by_default"],
                    options=self._rank_by_column_options(),
                    max_selections=5,
                    on_change=self._callbacks.query_rankby_changed)

def query_rankby_changed(self):
        if 'SERIAL_NUMBER' not in st.session_state.q_rank_by:
            alert_user(self._messenger, level='warning', msg="The rank-by argument must contain the 'SERIAL_NUMBER' column, adding it back in")
            st.session_state.q_rank_by.insert(0, 'SERIAL_NUMBER')

I know I could just hard-code SERIAL_NUMBER and only allow users to add to it, but I would like it visible, so the user knows it is being selected.

thx

2

I’m not sure how your larger class is structured, but this works for me:

import streamlit as st

def validate():
    if 'A' not in st.session_state.multiselect:
        st.session_state.multiselect = ['A']+st.session_state.multiselect

st.multiselect('Multiselect', ['A', 'B', 'C', 'D', 'E'],default='A', on_change=validate, key='multiselect')
3

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