Ezio and Sandro, thank you very much for your attention to this issue, and for helping me split it into manageable chunks! To answer the question about why "coverage" does not show as high a total as it ought: it's because coverage normally can't see the outer, global scope execution of modules that are already imported by the time "coverage" itself can take control and install a tracer. I have another patch outstanding that fixes this — we are still working on it, but the code works fine — if you want to run "coverage" and see a more accurate number: http://bugs.python.org/issue11561