Dynamically update the title in Dash Plotly

Question

I have created this very simplified example in which I would like to dynamically update the title of a chart as a dropdown label changes. Here's the code:

data = {'Stock': ['F',  'NFLX',  'AMZN'], 'Number': [10, 15, 7]}
df = pd.DataFrame(data, columns=['Stock', 'Number'])
stock_options = df['Stock']

app = dash.Dash(__name__)

app.layout = html.Div(children=[
    html.H1(children='Example Bar Chart'),
    html.Div([
        dcc.Dropdown(
            id='dropdown',
            options=[{'label': i, 'value': i} for i in stock_options],
            value='F',

         ),
        html.Div(dcc.Graph(id='graph')),
    ]),
])


@app.callback(
   Output(component_id='graph', component_property='figure'),
   Input(component_id='dropdown', component_property='value')
)
def update_graph(stock):
    msk = df.Stock.isin([stock])
    figure = px.bar(df[msk], x='Stock', y='Number', title=f"{stock} open price")

    return figure


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

So, while keeping the same label in dropdown instead of 'F open price' in the title I would like to get 'Facebook open price'... and so on. I've tried to solve this with map but I couldn't get it working. Can someone point me in the direction on how to resolve this? Thanks in advance.

Answer 1

As I wrote in my comment, not sure how you want to store the mapping between symbol name and the displayed title in the graph. Here is one solution that works using a dictionary stock_name_mapping that contains the symbols als keys and the displayed names as values:

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

import plotly.express as px

data = {'Stock': ['F',  'NFLX',  'AMZN'], 'Number': [10, 15, 7]}
df = pd.DataFrame(data, columns=['Stock', 'Number'])
stock_options = df['Stock']

stock_name_mapping = {'F': 'Facebook',
                      'NFLX': 'Netflix',
                      'AMZN': 'Amazon'}

app = dash.Dash(__name__)

app.layout = html.Div(children=[
    html.H1(children='Example Bar Chart'),
    html.Div([
        dcc.Dropdown(
            id='dropdown',
            options=[{'label': i, 'value': i} for i in stock_options],
            value='F',

         ),
        html.Div(dcc.Graph(id='graph')),
    ]),
])


@app.callback(
   Output(component_id='graph', component_property='figure'),
   Input(component_id='dropdown', component_property='value')
)
def update_graph(stock):
    msk = df.Stock.isin([stock])
    stock_name = stock_name_mapping[stock]
    figure = px.bar(df[msk], x='Stock', y='Number', title=f"{stock_name} open price")

    return figure


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