Create All option for multiselect

all_multiselect.py

import streamlit as st
import pandas as pd

def select_options():
    """Select options based on the user's selection and update the session state.

    This function is triggered when the selection of options changes. It checks if "All" is selected and updates
    the session state accordingly. If "All" is selected, it sets the selected options to all options except "All",
    and updates the maximum number of selections. If "All" is not selected, it updates the maximum number of selections
    based on the available options.

    Args:
        None

    Returns:
        None
    """
    if "selected_options" in st.session_state:
        if "All" in st.session_state["selected_options"]:
            st.session_state["selected_options"] = available_options[1:]
        st.session_state["max_selections"] = len(available_options) - 1
    else:
        st.session_state["selected_options"] = []
        st.session_state["max_selections"] = len(available_options) - 1

existing_genes = ["Gene1", "Gene2", "Gene3", "Gene4", "Gene5"]
clinvar_accession_ids = ["CLINVAR1", "CLINVAR2", "CLINVAR3", "CLINVAR4", "CLINVAR5"]
df = pd.DataFrame({"Gene": existing_genes, "Clinvar Accession ID": clinvar_accession_ids})

available_options = ["All"] + existing_genes

st.multiselect(
    label="Select a Gene",
    options=available_options,
    key="selected_options",
    max_selections=st.session_state["max_selections"],
    on_change=select_options,
    format_func=lambda x: "All" if x == "All" else x
)

if st.button("Clear Selection"):
    st.session_state["selected_options"] = []

selected_genes = available_options[1:] if st.session_state["max_selections"] == 1 else st.session_state["selected_options"]
filtered_df = df[df["Gene"].isin(selected_genes)]
st.dataframe(filtered_df)

My gist is a modification of the example from Carlos D. Serrano at https://medium.com/streamlit/multi-select-all-option-in-streamlit-3c92a0f20526.