How do I add circular labels to Plotly's pie chart?

Question

I have a code that generates a simple donut chart (technically, a pie chart) using Plotly.

import plotly.graph_objects as go


def main():
    labels = ["Yale blue", "Lemon chiffon",
              "Naples yellow", "Sandy brown", "Tomato"]
    values = [14, 15, 15, 18, 19]
    colors = ["#0D3B66", "#FAF0CA", "#F4D35E", "#EE964B", "#F95738"]
    fig = go.Figure(data=[go.Pie(labels=labels,
                                 values=values,
                                 hole=.7,
                                 direction="clockwise",
                                 sort=False)])
    fig.update_traces(marker=dict(colors=colors))
    fig.show()


if __name__ == "__main__":
    main()

For some reason, I want to add 12 circular labels to the plot: the first, located at 0:00, would say '1', the second, located at 1:00, would say '2' and so on. I would like to see something along those lines:

def add_circular_labels(fig: go.Figure,
                        labels: List[str]:
    ...
add_circular_labels(fig, ["1", "2", ...])

How could I achieve that?

Answer 1

An easy way would be to superimpose an empty polar plot on your pie chart. Then settings the ticks/grid as follows:

import plotly.graph_objects as go

labels = ["Yale blue", "Lemon chiffon",
            "Naples yellow", "Sandy brown", "Tomato"]
values = [14, 15, 15, 18, 19]
colors = ["#0D3B66", "#FAF0CA", "#F4D35E", "#EE964B", "#F95738"]
fig = go.Figure(data=[go.Pie(labels=labels,
                                values=values,
                                hole=.7,
                                direction="clockwise",
                                sort=False)])
fig.update_traces(marker=dict(colors=colors))

def add_circular_labels(fig: go.Figure, labels: list):
    fig.add_trace(go.Scatterpolar())
    fig.update_layout(
        polar = dict(
            radialaxis_visible=False,
            angularaxis = dict(
                type="category",
                categoryarray=labels,
                direction="clockwise",
                #rotation=90,
                showticklabels=True,
                ticks='', showgrid=False)
        )
    )

add_circular_labels(fig, list(range(1, 13)))
fig.show()

Output:

See the doc for details about layout.polar.