BUG: read_excel fails with IndexError: list index out of range

[YarShev]

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

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

• (optional) I have confirmed this bug exists on the master branch of pandas.

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Note: Please read this guide detailing how to provide the necessary information for us to reproduce your bug.

Code Sample, a copy-pastable example

# Your code here
import pandas
df = pandas.read_excel("excel_sheetname_title.xlsx")
IndexError: list index out of range

pandas : 1.2.0
numpy : 1.19.2
pytz : 2020.5
dateutil : 2.8.1
pip : 20.3.3
setuptools : 51.1.2.post20210112
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : None
IPython : None
pandas_datareader: None
bs4 : None
bottleneck : None
fsspec : None
fastparquet : None
gcsfs : None
matplotlib : None
numexpr : None
odfpy : None
openpyxl : 3.0.6
pandas_gbq : None
pyarrow : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : 2.0.1
xlwt : None
numba : None

The file which read_excel fails on.
excel_sheetname_title.xlsx

[asishm]

full traceback please.

I can't open this file with Excel (It tries to recover then fails)

[YarShev]

df = pandas.read_excel("excel_sheetname_title.xlsx")
Traceback (most recent call last):
File "", line 1, in
File "miniconda3\envs\pandas\lib\site-packages\pandas\util_decorators.py", line 299, in wrapper
return func(*args, **kwargs)
File "miniconda3\envs\pandas\lib\site-packages\pandas\io\excel_base.py", line 344, in read_excel
data = io.parse(
File "miniconda3\envs\pandas\lib\site-packages\pandas\io\excel_base.py", line 1153, in parse
return self._reader.parse(
File "miniconda3\envs\pandas\lib\site-packages\pandas\io\excel_base.py", line 479, in parse
sheet = self.get_sheet_by_index(asheetname)
File "miniconda3\envs\pandas\lib\site-packages\pandas\io\excel_openpyxl.py", line 498, in get_sheet_by_index
return self.book.worksheets[index]
IndexError: list index out of range

[YarShev]

I can't open this file with Excel (It tries to recover then fails)

Yes, I have the same issue. However, my excel recovered the file and I can open it.

[YarShev]

I have figured out why the exception is arisen. The file, which I provided, can be read via xlrd <= 1.2.0 (maybe via even other xlrd versions, but not >= 2.0). However, pandas 1.2.0 uses openpyxl to read the file, if it is installed, that leads to the exception.

[asishm]

yes, this is probably an openpyxl bug then.

In [131]: wb = openpyxl.load_workbook(path, read_only=False) # or read_only=True - which is what pandas actually uses, but it doesn't affect the results for this file

In [132]: wb.sheetnames
Out[132]: []

In [133]: wb.read_only
Out[133]: False

In [134]: wb.worksheets
Out[134]: []

wb.worksheets is an empty list and pandas does sheet = wb.worksheets[0] which is what fails with the IndexError. Maybe a better error message here?

[asishm]

did some digging - again - this is if anything an upstream issue.

openpyxl has this block of code:

# openpyxl/reader/excel.py in ExcelReader.read_worksheets
        for sheet, rel in self.parser.find_sheets():
            if rel.target not in self.valid_files: # this results in True for all the sheets
                continue

the if statement becomes True for all the sheets.
self.valid_files is this list

['_rels/',
 '_rels/.rels',
 '[Content_Types].xml',
 'docProps/',
 'docProps/app.xml',
 'docProps/core.xml',
 'xl/',
 'xl/workbook.xml',
 'xl/.DS_Store',
 '__MACOSX/xl/._.DS_Store',
 'xl/worksheets/',
 'xl/styles.xml',
 'xl/theme/',
 'xl/_rels/',
 'xl/sharedStrings.xml',
 'xl/worksheets/Sheet2.xml',
 'xl/worksheets/Sheet3.xml',
 'xl/worksheets/Sheet1.xml',
 'xl/worksheets/Sheet4.xml',
 'xl/theme/theme1.xml',
 'xl/_rels/workbook.xml.rels']

but the relationships file (rel.target) has the filenames of the sheets as lowercase

['xl/worksheets/sheet1.xml',
 'xl/worksheets/sheet2.xml',
 'xl/worksheets/sheet3.xml',
 'xl/worksheets/sheet4.xml']

This probably indicates this is a malformed excel file (given that Excel also tries to "fix" the errors) - so openpyxl may be doing the right thing. I don't particularly intend on reading up the specs as to whether these should be case sensitive or not.

Re-saving the zip after correctly capitalizing the 's' in 'sheetX.xml' in the rels file (xl/_rels/workbook.xml.rels) makes it readable.

[YarShev]

Yes, more accurate error message would be better.

[simonjayhawkins]

Thanks @YarShev for the report

since this worked in 1.1.5, i'll label as regression.

Yes, more accurate error message would be better.

further investigations/PRs welcome