I am trying to create a population pyramid graph using Dash with Plotly - python-3.x

Question

i have a directory containing three files, years.csv, 2014.csv and 2015.csv. i want to plot a population pyramid graph for the two files but i want pandas to pick the dataframe from the years.csv with respect to the slider value.
my years.csv looks like, on the slider when i select 2014, from the code you can see, its an int that i convert into a string and append .csv to it. but all i want is that final string interpreted as df = pd.read_csv('2014.csv') so that i can be able to generate graphs of all the years as long as that file is in the directoy.
years
0
2014(2014.csv)
1
2015(2015.csv)
from dash import Dash, dcc, html, Input, Output
# import plotly.express as px
import plotly.graph_objects as gp
import pandas as pd
# df = pd.read_csv('https://raw.githubusercontent.com/plotly/datasets/master/gapminderDataFiveYear.csv')
df = pd.read_csv('years.csv')
app = Dash(__name__)
app.layout = html.Div([
dcc.Graph(id='graph-with-slider'),
dcc.Slider(
df['year'].min(),
df['year'].max(),
step=None,
value=df['year'].min(),
marks={str(year): str(year) for year in df['year'].unique()},
id='year-slider'
)
])
#app.callback(
Output('graph-with-slider', 'figure'),
Input('year-slider', 'value'))
def update_figure(selected_year):
new_df = str(df[df.year == selected_year]) + ".csv"
print(new_df)
# fig = px.scatter(filtered_df, x="gdpPercap", y="lifeExp",
# size="pop", color="continent", hover_name="country",
# log_x=True, size_max=55)
y_age = new_df['Age']
x_M = new_df['Male']
x_F = new_df['Female'] * -1
# fig.update_layout(transition_duration=500)
# Creating instance of the figure
fig = gp.Figure()
# Adding Male data to the figure
fig.add_trace(gp.Bar(y= y_age, x = x_M,
name = 'Male',
orientation = 'h'))
# Adding Female data to the figure
fig.add_trace(gp.Bar(y = y_age, x = x_F,
name = 'Female', orientation = 'h'))
# Updating the layoutout for our graph
fig.update_layout(title = 'Population Pyramid of Uganda-2015',
title_font_size = 22, barmode = 'relative',
bargap = 0.0, bargroupgap = 0,
xaxis = dict(tickvals = [-600000, -400000, -200000,
0, 200000, 400000, 600000],
ticktext = ['6k', '4k', '2k', '0',
'2k', '4k', '6k'],
title = 'Population in Thousands',
title_font_size = 14)
)
# fig.show()
return fig
if __name__ == '__main__':
app.run_server(debug=True)