Python real reload stripped from ipython autoreload extension.
Does not change identity after reloading, which should be a good thing.
Does not update module variables, which may or may not be a good thing.
Mental comparison with builtin reload and ipython autoreload:
- builtin reload: get new, use new and discard old.
- autoreload: get new, update old using new, use both updated old and new.
- retroreload: get new, update old using new, use updated old and discard new.