The problem I've noticed is that if I append the file with each of the 100k runs (one at a time), it can happen that two threads try to save to the file at the same time and some row (s) end up empty.

Microsoft is integrating Python into its Excel app. A public preview is available for Microsoft 365 subscribers now and all the Python code runs on the Microsoft Cloud.

Microsoft today announced the public preview of Python in Excel, which will allow advanced spreadsheet users to combine scripts in the popular Python language and their usual Excel formulas in the ...

This will enable users to perform complex statistical analysis, advanced visualizations, predictive analytics, and machine learning in Excel.