Sorting a large CVS file

[ichabod801]

I need to separate out all the rows with a given id.

What do you need to do? Do you need to separate out the rows with a given ID, or do you need to sort by the ID? You appear to already have the rows for a particular ID. To sort by that ID you would use sort_index:

pacto.sort_index(by = 'individual-local-identifier')

You may also want to look at the groupby method.