Callback function not using the source file to update the graph - pandas

Question

Im using a csv file as my data source. I want the graph to update based on the radio button selection i make, please find my source code below.
import pandas as pd
import numpy as np
import plotly.graph_objs as go
import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input,Output
df = pd.read_csv('population2.csv')
fst_yvalues = df['PopEstimate2010']/1000000
scd_yvalues = df['PopEstimate2011']/1000000
trd_yvalues = df['PopEstimate2012']/1000000
app = dash.Dash()
app.layout = html.Div(children=[
html.H1('My first Interactive Graph'),
html.Div(dcc.RadioItems(id='radio_items',
options=[{'label':'PopEstimate2010','value':'pop2010'},
{'label':'PopEstimate2011','value': 'pop2011'},
{'label':'PopEstimate2011' ,'value':'pop2012'}],
value='pop2010')),
html.Br(),
html.Div(children=[
dcc.Graph(id='int_bar')])])
#app.callback(Output('int_bar','figure'),[Input('radio_items','value')])
def bar_chart(value):
trace = []`
if value == 'pop2010':
trarce = [go.Bar(x=df['Name'],y=fst_yvalues)]
elif value == 'pop2011':
trarce = [go.Bar(x=df['Name'],y=scd_yvalues)]
else:
trarce = [go.Bar(x=df['Name'],y=trd_yvalues)]
layout = go.Layout(title='MY FIRST GRAPH',
xaxis=dict(title='MY X-AXIS'),
yaxis=dict(title='MY Y-AXIS'),hovermode='closest')
figure = go.Figure(data=trace,layout=layout)enter code here
return figure
if __name__ == '__main__':
app.run_server(debug=True)
When i try to run this, it only gives me the layout but not the actual graph.

Answer 1

Below is the approach i have taken to get this to work :
#app.callback(Output('int_bar','figure'),[Input('radio_items','value')])
def make_bar_chart(value):
if value == 'pop2010':
figure = {'data': [go.Bar(x=df['Name'],y=fst_yvalues)],
'layout': go.Layout(title='MY FIRST GRAPH',
xaxis=dict(title='MY X-AXIS'),
yaxis=dict(title='MY Y-AXIS'),hovermode='closest')
}
...
...
return figure
if __name__ == '__main__':
app.run_server(debug=True)