How to split a huge csv file based on content of first column?

Question

• I have a 250MB+ huge csv file to upload
• file format is group_id, application_id, reading and data could look like

Answer 1

If the rows are sorted by group_id, then itertools.groupby would be useful here. Because it's an iterator, you won't have to load the whole file into memory; you can still write each file line by line. Use csv to load the file (in case you didn't already know about it).