Update app.py

app.py

@@ -0,0 +1,26 @@
+from dash import Dash, html, dcc, callback, Output, Input
+import plotly.express as px
+import pandas as pd
+import os
+
+df = pd.read_csv('https://raw.githubusercontent.com/plotly/datasets/master/gapminder_unfiltered.csv')
+app = Dash(__name__)
+server = app.server  # Important for deployment
+
+app.layout = [
+    html.H1(children='Title of Dash App', style={'textAlign':'center'}),
+    dcc.Dropdown(df.country.unique(), 'Canada', id='dropdown-selection'),
+    dcc.Graph(id='graph-content')
+]
+
+@callback(
+    Output('graph-content', 'figure'),
+    Input('dropdown-selection', 'value')
+)
+def update_graph(value):
+    dff = df[df.country==value]
+    return px.line(dff, x='year', y='pop')
+
+if __name__ == '__main__':
+    port = int(os.environ.get('PORT', 7860))
+    app.run(host='0.0.0.0', port=port, debug=False)