Used ERA5_2023_analysis.ipynb to merge 365 csv files from "C:\GIIS\ERA 5 Hourly 2023\Python code\Code\ERA5_2023" folder to make it one single csv format. Then used same code to add new columns year, ...

This is not correct. The correct behavior would be for Python to throw a ValueError, specifying the mismatch in array shapes. Indeed, this is the behavior if B is anything but a column or row matrix.

Microsoft is adding the Python programming language to Microsoft Excel, allowing users to create powerful functions for analyzing and manipulating data. The public preview of the feature is now ...