OK, by my own rules that means it's "written in Python" then. But in that case what I actually meant is that majority of time in calls to zipfile is spent in pu

OK, by my own rules that means it's "written in Python" then. But in that case what I actually meant is that majority of time in calls to zipfile is spent in pure C, not in the Python interpreter loop, and if it's based on zlib then that agrees with what I meant. (There is an exception I didn't mention: if the zip is encrypted then the zipfile module falls back to pure Python code. The difference is very noticeable!)