Using selectbox / multiselect box unable to select a value

I am running my app in local, After submit button I want to select a value from the select box but value in not available. please find the sample code

import streamlit as st

s_d_user = st.sidebar.selectbox(
                "Select User",
dd = st.sidebar.button("Submit", type="primary")

if dd:

    l_users_name = [1,2,3,4]
    s_selected_user = st.selectbox(
                "Select User",

When the app launch:

After selecting value:

Buttons aren’t stateful. Nesting widgets inside a button is almost never what you want.

Check out Button behavior and examples to see some explanations and code snippets that cover some common scenarios.