import streamlit as st
import pandas as pd
import numpy as np
import altair as alt

chart_data = pd.DataFrame(
    np.random.randn(20, 3),
    columns=['a', 'b', 'c'])

chart_placeholder = st.empty()

color = st.radio("select color", ('a', 'b', 'c'))
c = alt.Chart(chart_data).mark_circle().encode(
    x='a', y='b', size='c', 
    #color='c', tooltip=['a', 'b', 'c'],
color = alt.value(color))
st.altair_chart(c, use_container_width=True)
chart_placeholder.altair_chart(c)