xml.etree.ElementTree iterparse（）仍然使用大量内存？

I've been experimenting with iterparse to reduce the memory footprint of my scripts that need to process large XML docs. Here's an example. I wrote this simple script to read a TMX file and split it into one or more output files not to exceed a user-specified size. Despite using iterparse, when I split a 886MB file into 100MB files, the script runs away with all available memory (grinding to a crawl at using 6.5 of my 8MB).I've been experimenting with iterparse to reduc