app.py

# INSTRUCTIONS:
# 1. Open a "Terminal" by: View --> Terminal OR just the "Terminal" through the hamburger menu
# 2. run in terminal with: streamlit run test_altair_streamlit.py
# 3. click the "Open in Browser" link that pops up OR click on "Ports" and copy the URL
# 4. Open a Simple Browswer with View --> Command Palette --> Simple Browser: Show
# 5. use the URL from prior steps as intput into this simple browser


import streamlit as st
import altair as alt
from vega_datasets import data
 
st.title('My First Streamlit App')

source = data.seattle_weather()

scale = alt.Scale(
    domain=["sun", "fog", "drizzle", "rain", "snow"],
    range=["#e7ba52", "#a7a7a7", "#aec7e8", "#1f77b4", "#9467bd"],
)
color = alt.Color("weather:N", scale=scale)

# We create two selections:
# - a brush that is active on the top panel
# - a multi-click that is active on the bottom panel
brush = alt.selection_interval(encodings=["x"])
click = alt.selection_point(encodings=["color"])

# Top panel is scatter plot of temperature vs time
points = (
    alt.Chart()
    .mark_point()
    .encode(
        alt.X("monthdate(date):T", title="Date"),
        alt.Y(
            "temp_max:Q",
            title="Maximum Daily Temperature (C)",
            scale=alt.Scale(domain=[-5, 40]),
        ),
        color=alt.condition(brush, color, alt.value("lightgray")),
        size=alt.Size("precipitation:Q", scale=alt.Scale(range=[5, 200])),
    )
    .properties(width=550, height=300)
    .add_params(brush)
    .transform_filter(click)
)

# Bottom panel is a bar chart of weather type
bars = (
    alt.Chart()
    .mark_bar()
    .encode(
        x="count()",
        y="weather:N",
        color=alt.condition(click, color, alt.value("lightgray")),
    )
    .transform_filter(brush)
    .properties(
        width=550,
    )
    .add_params(click)
)

chart = alt.vconcat(points, bars, data=source, title="Seattle Weather: 2012-2015")

tab1, tab2 = st.tabs(["Streamlit theme (default)", "Altair native theme"])

with tab1:
    st.altair_chart(chart, theme="streamlit", use_container_width=True)
with tab2:
    st.altair_chart(chart, theme=None, use_container_width=True)