import streamlit as st




derf update():
    update_time = int(time.time())
    if update_time % 2 == 0:
        
        place_holder.text("before")
    else:
        place_holder.text("after")

def main():
    
    st.title("App")
    while True:
        place_holder = st.empty()
        up = update()
if __name__  == "__main__":
    main()