reading multiple large root files (each of about 1GB) trying to read each file at a time to pandas df for groupby operation

[sbdrchauhan]

I know to open large files, it is best to use uproot.iterate() with step_size option. But step_size is different for each file. I want to do the operation for each eventID, so I want to make pandas dataframe to perform analysis for each groupby object for each eventID. If I use some fixed step_size, won't it chop off the dataframe in the middle of the event, and I won't be able to do groupby analysis as it chops not at every eventID.

Something like this:

here calculateUVW() method should get dataframe for each eventID, but step_size might chop off in the middle of eventID and my analysis might be incorrect.

Thank you