I am trying to learn Python (day 2) and am hoping to practice with Excel books first as this is where I am comfortable/fluent.

Right off the bat I am having an error that I don't quit understand when running the below code:

import openpyxl

wb = openpyxl.load_workbook("/Users/Scott/Desktop/Workbook1.xlsx")

print(wb.sheetnames)

This does print my sheet names as requested, but it is followed by:

/Users/Scott/PycharmProjects/Excel/venv/lib/python3.7/site-packages/openpyxl/worksheet/_reader.py:293: UserWarning: Unknown extension is not supported and will be removed
  warn(msg)

I have found other questions that point to slicers/conditional formatting etc, but that does not apply here. This is a book I just made and only added 3 sheets before saving. It has no data, no formatting, and the extension is valid. I have no add-ons installed on my excel either.

Any idea why why I am getting this error? How do I resolve?

Python: 3.7
openpyxl: 2.6

I had a similar issue. I developed an application which read and write Excel files. It woked well on my Windows computer, but then I tried to run it on a friends mac. It showed the same error. I could "fix" it by changing the configuration of the workbook, like this:

import openpyxl as op

wb = op.load_workbook(file, read_only=True, data_only=True)

But, as you can see, you can only read Excel files with this configuration. At the end, I realized that my friend didn't have Microsoft Office installed on his computer. Install it truly solved my problem.