openpyxl_encode_error.py

from openpyxl import Workbook

text = "￿" # Including three bytes: hexadecimal FFBFBF   resulting ValueError
# text = '\x16'                                        # resulting IllegalCharacterError

wb = Workbook()
ws = wb.active
ws.append([text])
wb.save("test.xlsx")

pandas_encode_error.py

"""FFBFBF 3 bytes in text prevents excel to be saved"""

from io import BytesIO
import platform
import sys

import pandas as pd

print(pd.__version__)
print(platform.platform())
print(sys.version)

"""
pandas version: 1.5.3
Windows-10-10.0.22631-SP0
Python 3.11.0 (main, Oct 24 2022, 18:26:48) [MSC v.1933 64 bit (AMD64)]

and

openpyxl                 3.1.2
pandas                   2.2.1
Linux-6.11.5-200.fc40.x86_64-x86_64-with-glibc2.39 (Fedora)
Python 3.12.7 (main, Oct  1 2024, 00:00:00) [GCC 14.2.1 20240912 (Red Hat 14.2.1-3)]
"""

df = pd.DataFrame(data=dict(a=["text 1", "text￿2"]))
output = BytesIO()
writer = pd.ExcelWriter(output, engine='openpyxl')
df.to_excel(writer, index=False, sheet_name="first_sheet")
writer.close()