This may not be a problem with openpyxl, but since Excel (2008 for Mac) can read the file successfully, I thought I would report it.
Openpyxl blows up (trace below) when reading this file, but if I open and re-save it with MS Excel, openpyxl can, not surprisingly, read the rewritten file with no problems.
The metadata for this file suggests that it was created by a product using the Axolot Data XLSReadWriteII library (v 4.00.38).
Unfortunately I am not permitted to provide the file, and I have no way of creating a file that reproduces the problem. This may be a bug in the Axolot library; the current version of that is 4.00.66.
File "/Users/johnbigboote/Documents/code/python/pcgc-env/lib/python2.7/site-packages/openpyxl/reader/excel.py", line 115, in load_workbook _load_workbook(wb, archive, filename, use_iterators) File "/Users/johnbigboote/Documents/code/python/pcgc-env/lib/python2.7/site-packages/openpyxl/reader/excel.py", line 140, in _load_workbook wb.properties.excel_base_date = read_excel_base_date(xml_source=archive.read(ARC_WORKBOOK)) File "/Users/johnbigboote/Documents/code/python/pcgc-env/lib/python2.7/site-packages/openpyxl/reader/workbook.py", line 82, in read_excel_base_date if ('date1904' in wbPr.keys() and wbPr.attrib['date1904'] in ('1', 'true')): AttributeError: 'NoneType' object has no attribute 'keys'
Random asides: your issues form needs updating: not all versions appear in the Version dropdown. Also, I can't search by Version in the issues search form. Also, I didn't notice any release notes/change log information anywhere for openpyxl.