app.py

import dash
from dash.dependencies import Input, Output
import dash_core_components as dcc
import dash_html_components as html
import plotly.express as px

gapminder = px.data.gapminder().query("year == 2007")

input_figure = px.scatter(gapminder, x="gdpPercap", y="lifeExp", size="pop",
          custom_data=[gapminder.index], # this is the special bit!
          log_x=True, size_max=60, height=400).update_layout(dragmode='lasso')

app = dash.Dash(__name__)

app.layout = html.Div([dcc.Graph(id='input-figure', figure=input_figure),
                      dcc.Graph(id='output-figure')])

@app.callback(Output('output-figure', 'figure'),
    [Input('input-figure', 'selectedData')])
def display_selected_data(selectedData):
    df = gapminder
    if selectedData:
        indices = [point["customdata"][0] for point in selectedData["points"]]
        df = df.loc[indices]

    return px.scatter_geo(df, locations="iso_alpha", size="pop", height=400)


if __name__ == '__main__':
    app.run_server(debug=True)