Чтение в Excel с использованием pandas и запись в формате Excel с использованием xlsxwriter

Question

Код ниже работает нормально:

import re
import xlsxwriter

workbook = xlsxwriter.Workbook('test.xlsx')
worksheet = workbook.add_worksheet()
bold = workbook.add_format({'bold': True, 'color': 'red'})

# Some sample test data.
string = 'A best is the best'
command = 'best'
regex  = r'(' + command + ')'
segments = re.split(regex, string)

if len(segments) == 1:
        # String doesn't have a match, write as a normal string.
        worksheet.write(0, 0, string)
else:
        # Iternate through the segments and add a format before the matches.
        tmp_array = []
        for segment in segments:
            if segment == command:
                # Add a bold format before the matched word.
                tmp_array.append(bold)
                tmp_array.append(segment)
            elif not segment:
                # Ignore blank segments.
                pass
            else:
                tmp_array.append(segment)

        worksheet.write_rich_string(0, 0, *tmp_array)
workbook.close()

Теперь я хочу прочитать данные из test.xlsx с помощью pandas и применить форматирование к этим данным с помощью xlsxwriter, а затем сохранить данные в новом Excel testNew.xlsx. Я следовал за этой статьей . Вот мой код, который работает не так, как ожидалось:

import xlsxwriter
import pandas as pd
import re


df = pd.read_excel(r'C:\Users\test.xlsx')

# Create a Pandas Excel writer using XlsxWriter as the engine.
writer = pd.ExcelWriter('testNew.xlsx',  engine ='xlsxwriter') 
# Convert the dataframe to an XlsxWriter Excel object
df.to_excel(writer, sheet_name='Sheet1')
# Get the xlsxwriter objects from the dataframe writer object.
workbook  = writer.book
worksheet = writer.sheets['Sheet1']

# Set up some formats to use.
blue = workbook.add_format({'color': 'blue'})

command = 'best'
string = df.iat[0,0] #########THROWS ERROR################

regex  = r'(' + command + ')'
segments = re.split(regex, string)

if len(segments) == 1:
        # String doesn't have a match, write as a normal string.
    worksheet.write(0, 0, string)
else:
    # Iternate through the segments and add a format before the matches.
    tmp_array = []
    for segment in segments:
        if segment == command:
                tmp_array.append(blue)
                tmp_array.append(segment)
        elif not segment:
                # Ignore blank segments.
            pass
        else:
            tmp_array.append(segment)

    worksheet.write_rich_string(0, 0, *tmp_array)
writer.save()

Он выдает ошибку ниже:

Exception has occurred: IndexError
index 1 is out of bounds for axis 0 with size

Что я здесь не так делаю?