It'd be very useful if python-docx produced identical binary result every time a document with identical contents is being generated.

I have two specific scenarios in mind here:

• keeping documentation for some slow-changing data in version control without wasting space every time a report is regenerated,
• being able to quickly check binary hash of a report to verify the same contents were generated as a kind of unit test

Unfortunatelly the current code produces binary different .docx every time the python script is executed.

I've looked into the issue and propose a pull request to satisfy the need.

Last but not least, thanks for your great library, I am glad I can give something back.