I use the xlrd module in Python scripts to extract data from Excel workbooks. You can use the Python xlrd module to list the worksheets in a workbook and you can use the xlrd.sheet "visibility" value to determine whether a sheet is hidden and, if it is hidden, whether a user can unhide the sheet. The value should be either 0, 1, or 2 with the numbers having the following meaning:
Visibility of the sheet:
0 = visible
1 = hidden (can be unhidden by user -- Format -> Sheet -> Unhide)
2 = "very hidden" (can be unhidden only by VBA macro)
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