Notes for packagers of Python3 ============================== 0. Faster build turnaround -------------------------- By default, python builds with profile-guided optimization. This needs an additional run of the test suite and it is generally slow. PGO build takes around 50 minutes. For development, use "--without profileopt" option to disable PGO. This shortens the build time to ~5 minutes including test suite. 1. import_failed.map ---------------------- This is a mechanism installed as part of python3-base, that places shim modules on python's path (through a generated zzzz-import-failed-hooks.pth file, so that it is imported as much at the end as makes sense; and an _import_failed subdir of /usr/lib/pythonX.Y). Then when the user tries to import a module that is part of a subpackage, the ImportError will contain a helpful message telling them which missing subpackage to install. This can sometimes cause problems on non-standard configurations, if the pth gets included too early (for instance if you are using a script to include all pths by hand in some strange order). Just something to look out for.