It's not too hard actually. A line of python is roughly 80x slower than a line of C (no exaggeration). But a typical line of python does a lot more than a typ

It's not too hard actually. A line of python is roughly 80x slower than a line of C (no exaggeration). But a typical line of python does a lot more than a typical line of C. So things you can do with a "loose" loop (like once per 64k block) is usually ok in python. Things you have to do with a "tight" loop (like once per byte) need to be in C. I once did a presentation about python performance optimization lessons from bup: http://lanyrd.com/2011/pycodeconf/sghxk/ http://lanyrd.com/2011/pycodeconf/sghxk/ And it's true, I'm not the most active maintainer anymore. The people who took over seem to be doing a pretty good job though.