Annotations in the center of Donut Subplots

📊 Plotly Python
1

I am having issues adding an annotation in the center of each donut in a facet. I can seem to get the annotation centered in one facet, but not automatically in the others. In the example below, I just have one row, but I also have the same issue when having multiple rows. Is there a way to do this or another approach I should be taking?

import pandas as pd
import psycopg2
from sqlalchemy import create_engine, URL 
import plotly.graph_objects as go
import plotly.express as px
from plotly.subplots import make_subplots
from plotly import tools
import plotly.offline as pyo
import dash

year = ['2021', '2022', '2023', '2021', '2022', '2023', '2021', '2022', '2023']
answer_cat = ['Promoters', 'Promoters', 'Promoters', 'Passives', 'Passives', 'Passives', 'Detractors', 'Detractors', 'Detractors']
unique_cnt = [778, 871, 432, 407, 476, 324, 126, 147, 104]

dict_d = {'year': year, 'answer_cat': answer_cat, 'unique_cnt': unique_cnt} 
   
df = pd.DataFrame(dict_d)

fig = px.pie(df, 
             values='unique_cnt', 
             names='answer_cat',
             facet_col='year',
             color='answer_cat',
             hole=.55,
             category_orders={'year': ['2021', '2022', '2023'],
                              'answer_cat': ['Promoters', 'Passives', 'Detractors']
                             },
             color_discrete_map={'Promoters':'lightgreen', 
                                 'Passives':'lightgrey', 
                                 'Detractors':'#FF474C'},
             height=400, width=1800
            )

fig.update_traces(hoverinfo='label+percent', texttemplate='%{percent}', textfont_size=14, textposition='outside',
                  marker=dict( line=dict(color='#FFFFFF', width=2)))
fig.for_each_annotation(lambda a: a.update(text=a.text.split("=")[-1]) )

fig.update_layout(legend=dict(
    orientation="h",
    entrywidth=70,
    yanchor="bottom",
    y=-.25,
    xanchor="center",
    x=.5
))

# Add total value in the center of each subplot's donut hole
total_subplots = len(['2021', '2022', '2023'])
subplot_width = 0.33125

for i, year_val in enumerate(['2021', '2022', '2023']):
    total_value = df[df['year'] == year_val]['unique_cnt'].sum()
    nps_promoters = df[(df['year'] == year_val) & (df['answer_cat'] == 'Promoters')]['unique_cnt'].sum() 
    nps_detractors = df[(df['year'] == year_val) & (df['answer_cat'] == 'Detractors')]['unique_cnt'].sum() 
    nps_score = (((nps_promoters)/(total_value) - (nps_detractors)/(total_value) ) * 100).round(1)
    text_str = '<span style="font-size: 16px;"><b>' + str(nps_score) + '</b></span><br><span style="font-size: 12px;">(' + str(total_value) + ')</span>'
    
    # Calculate the x position based on the subplot width and index
    x_position = (i + 0.5125) * subplot_width
    # x_position = (i * subplot_width) + (subplot_width / 2)
    # x_position = (i * subplot_width) + (subplot_width / 2) + (subplot_width / (2 * total_subplots)) - (0.5 * subplot_width)
    # x_position = (i * subplot_width) + (subplot_width / 2) + (subplot_width / (2 * total_subplots)) - (subplot_width / 2)
    # x_position = (i * subplot_width) + (subplot_width / 2) + (subplot_width / (2 * total_subplots))
    # x_position = (i * subplot_width) + (subplot_width / 2) + (subplot_width / total_subplots)
    
    fig.add_annotation(
        xref="paper",
        yref="paper",
        x=x_position,
        y=0.5,
        text=(text_str),
        showarrow=False
    )

fig.show()```

![NPS - Center Issue|690x153](upload://yoGnEzJgWPelKpJ6S4fms71H0pw.png)