How to get radio items in drop down list?

Dash Python
1

I want when I select any region from the radio items, drop down list show the countries of that region. I share code below. Please make changes in the below code to get countries of specific region in the drop down list.

import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output
import plotly.graph_objs as go
import pandas as pd



terr2 = pd.read_csv('modified_globalterrorismdb_0718dist.csv')

region = terr2['region_txt'].unique()
country = terr2['country_txt'].unique()


app = dash.Dash(__name__,)
app.layout = html.Div([

html.Div([
        dcc.RadioItems(options=[
            {'label': k, 'value': k} for k in region
                 ], value='North America', id="radio_items"),

        html.Label(['Select Country:'], style={'color': 'white'}),
        dcc.Dropdown(id='w_countries',
                     multi=False,
                     clearable=True,
                     disabled=False,
                     style={'display': True},
                     value='Iraq',
                     placeholder='Select Countries',
                     options=[{'label': c, 'value': c}
                              for c in country])

         ], style={'margin-left': '5.4%', 'width': '20.4%', 'display': 'inline-block'}),

 ], style={'background-color': '#272B30'})

@app.callback(
    Output('w_countries', 'options'),
    Input('radio_items', 'value'))
def set_cities_options(selected_country):
    return [{'label': i, 'value': i} for i in country[selected_country]]

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