Since upgrading to openpyxl 2.4.0, my generated xlsx files aren't fully readable in Mac OS X 'Numbers' and 'Preview' apps.
See attached program 'zz00.py'. This program generates output file 'zz00.xlsx'. When I open 'zz00.xlsx' with 'Microsoft Excel 2008 for Mac' and LibreOffice, I can see the data okay. However, when I open the same file with my Mac's built-in Numbers or Preview apps, I can't see any data.
Based on my experience with my full-sized program, I believe this problem did not exist in openpyxl 2.3.5.
Mac OS X 10.11.6
Built-in Python 2.7.10
IDE: Visual Studio Code with Python extension, executing native Python 2.7.10