BUG: openpyxl 3.1.1 breaks pandas read_excel

[jonathanloske]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

import pandas as pd

file = ...

pd.read_excel(
  io=BytesIO(file.file.read()),
  sheet_name="sheet_name",
  header="header"
)

Issue Description

Since openpyxl 3.1.1, the code given above results in the following error:

Failed to process file: 'ReadOnlyWorksheet' object has no attribute 'defined_names'

Downgrading to openpyxl 3.1.0 fixes this issue. From the outside, it is not clear whether pandas or openpyxl needs to be fixed, even though it looks like a bug on openpyxl side. It is likely related to this issue which was marked as fixed in openpyxl 3.1.1: https://foss.heptapod.net/openpyxl/openpyxl/-/issues/1947

Link to openpyxl changelog: https://openpyxl.readthedocs.io/en/stable/changes.html#id1

There is also a report on StackOverflow which has already gotten more than 4000 views: https://stackoverflow.com/questions/75440354/why-does-pandas-read-excel-fail-on-an-openpyxl-error-saying-readonlyworksheet

Expected Behavior

reading a file works just like with openpyxl 3.1.0

Installed Versions

INSTALLED VERSIONS ------------------ commit : 2e218d1 python : 3.11.1.final.0 python-bits : 64 OS : Darwin OS-release : 22.3.0 Version : Darwin Kernel Version 22.3.0: Mon Jan 30 20:38:37 PST 2023; root:xnu-8792.81.3~2/RELEASE_ARM64_T6000 machine : x86_64 processor : i386 byteorder : little LC_ALL : None LANG : en_US.UTF-8 LOCALE : en_US.UTF-8

pandas : 1.5.3
numpy : 1.24.2
pytz : 2020.5
dateutil : 2.8.2
setuptools : 67.3.3
pip : 22.3.1
Cython : None
pytest : 7.2.1
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : 1.1
pymysql : None
psycopg2 : 2.9.5
jinja2 : 3.1.2
IPython : None
pandas_datareader: None
bs4 : None
bottleneck : None
brotli : None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : None
numba : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : None
snappy : None
sqlalchemy : 1.4.46
tables : None
tabulate : None
xarray : None
xlrd : None
xlwt : None
zstandard : None
tzdata : None

[phofl]

Hi, thanks for your report. We have already an issue for this, bug is indeed in openpyxl and not on our side

[jonathanloske]

This is the issue that tracks this: #51392