How I would (Like To) Change Import

PyCon 2008 lightning talk

Transcript

1. How I Would (Like To) Change Import Brett Cannon PyCon 2008 Lightning Talk
2. __import__()’s API sucks • local argument is not used. • Only two keys out of globals matters. • fromlist only there for opcodes. • Going to complain about this later. • Parser can split on dots, so why make the function do it?
3. How I would change it • name • Tuple of names, with each item a package level. • Empty strings/None represent a dot. • Removes need for level. • Still not sure if I like its removal, though.
4. • importer_name •globals[‘__name__’] • importer_path •globals[‘__path__’]
5. If I can’t change it ... • A saner API wrapper in the imp module. • Do people like having control over whether the top-level or specified module is returned?
6. sys.meta_path under-utilized • Nothing put here by default. • Yet really handy to use for control/ customization.
7. sys.meta_path defaults • Theoretically, sys.modules. • But probably too much of a special-case. • Built-in modules. • Frozen modules. • Extension modules. • .py/.pyc modules. • Ditch sys.path_hooks, sys.path_importer_cache.
8. Unfortunately ... • Changes what takes precedence in choosing what to import. • Currently searched by location on sys.meta_path/sys.path, then type of module. • Proposal would reverse this.
9. I don’t like sys.meta_path/sys.path • I would rather have a single, unified approach to having importers. • Stuff on sys.meta_path already knows whether it cares about its path argument or not.
10. How I would change it • sys.importers • Almost exactly like sys.meta_path. • path argument always given. • __path__ of parent or sys.path. • Treat path as a “suggestion” of where to look, with sys.path the default suggestion.
11. loader.load_module() over-burdened • Has to deal with sys.modules for reloading. • But that’s there only to support reload(). • ... which is no longer a built-in in Py3k. • Has to set various values on module that were already known to import.
12. Not sure how I would change it • Pass in a module to load_module()? • With PEP 3121 this might make creating a new module blindly a waste.
13. What __import__() returns is complicated • Depends on the value of fromlist. • Mostly there for the benefit of import- specific opcodes. • But shouldn’t the opcodes just deal with their own stuff?
14. Always return the same thing • Opcode to import a module. • Opcode to return the top-level module. • For ``import monty``. • Opcode to handle a list of specifc things to import. • For ``from monty import eels, hovercraft``.