app.py

import streamlit as st
import pandas as pd

astations = [
	["hongkongobservatory","HKO",22.3022566,114.1722662,"Hong Kong Observatory"],
	["kingspark","KP",22.3115408,114.1685675,"Observatory Meteorological Station, King's Park"],
]

acontainer1 = st.empty()
acontainer2 = st.empty()

def aoptionchange(aparam):
	acontainer2.write(aparam)
adf = pd.DataFrame(
	astations,
	columns=['akey','astationcode','alatitude','alongitude','atitle',]
)
aoption = acontainer1.selectbox(
	'Which station?',
	adf['atitle'],
	on_change=aoptionchange,
	args={'aselectedindex':index,}
)