按行数拆分数据框

I have a dataframe made up of 400'000 rows and about 50 columns. As this dataframe is so large, it is too computationally taxing to work with. I would like to split this dataframe up into smaller ones, after which I will run the functions I would like to run, and then reassemble the dataframe at the end. I have a dataframe made up of 400'000 rows and