python plotly dash treemap get selected child label

Question

I'm trying to use a plotly treemap within dash. When the user selects a subgroup in the treemap by clicking on it, the treemap zooms in on the selected section. Is there a way for me to get the user's selection and use that as an input into a Dash callback?

For example, here is code for a treemap in Dash:

import dash
import dash_core_components as dcc
import dash_html_components as html

import plotly.graph_objects as go

fig = go.Figure(go.Treemap(
    labels = ["Eve","Cain", "Seth", "Enos", "Noam", "Abel", "Awan", "Enoch", "Azura"],
    parents = ["", "Eve", "Eve", "Seth", "Seth", "Eve", "Eve", "Awan", "Eve"],
    root_color="lightgrey"
))

fig.update_layout(margin = dict(t=50, l=25, r=25, b=25))

app = dash.Dash()
app.layout = html.Div([
    dcc.Graph(figure=fig)
])

app.run_server(debug=True, use_reloader=False)  # Turn off reloader if inside Jupyter

And what I'd like to do would look something like this:

@app.callback(
    dash.dependencies.Output('some_other_figure', 'figure'),
    [
     dash.dependencies.Input('treemap_child_selection', 'value'),
     ]
)
def update_other_figure(treemap_selection):
    pass

Answer 1

You could use the dcc.Graph 's clickData property in your callback

clickData (dict; optional): Data from latest click event. Read-only.

@app.callback(
    dash.dependencies.Output("output", "children"),
    dash.dependencies.Input("graph", "clickData"),
)
def update_other_figure(click_data):
    print(click_data)
    # Do something with the data...

On clicking Noam in your example the value of click_data is

{'points': [{'curveNumber': 0, 'pointNumber': 4, 'currentPath': 'Eve/Seth/', 'root': 'Eve', 'entry': 'Eve', 'percentRoot': 0.16666666666666666, 'percentEntry': 0.16666666666666666, 'percentParent': 0.5, 'parent': 'Seth', 'label': 'Noam'}]}

You could retrieve the value of label from this and do something with it.

Answer 2

For me it take some time to understund the dict structure. I put here syntax to get correct value from click_data

click_data["points"][0]["label"]