main.py

import streamlit as st
import pandas as pd

def main():
    st.title("Cities Explorer!")

    cities = load_cities()

    populations = cities.groupby('state_id', as_index=False)['population'].sum()
    st.bar_chart(populations, x='state_id', y='population')

    states = cities['state_id'].unique()
    states.sort()

    state_selected = st.selectbox("Pick a state", states, )
    state_cities = cities[ cities['state_id'] == state_selected ].sort_values('city_ascii')
    state_population = state_cities['population'].sum()
    state_cities['population_scale'] = state_cities['population'] / state_population * 10000 + 1000
    st.bar_chart(state_cities, x='city_ascii', x_label='City', y='population', y_label='Population')
    st.map(state_cities, latitude='lat', longitude='lng', size='population_scale')

@st.cache_data
def load_cities():
    cities = pd.read_csv("./uscities.csv")
    return cities

if __name__ == "__main__":
    main()