Oh, I'm shame myself. Only when `from email import *` is used, __all__ submodules are imported. INADA Naoki <songofaca...@gmail.com>
On Mon, Sep 11, 2017 at 12:17 PM, Guido van Rossum <gu...@python.org> wrote: > I don't think submodules are automatically imported, unless there are import > statements in __init__.py. > > On Sun, Sep 10, 2017 at 8:08 PM, INADA Naoki <songofaca...@gmail.com> wrote: >> >> It looks simple and easy to understand. >> >> To achieve lazy import without breaking backward compatibility, >> I want to add one more rule: When package defines both of __getattr__ and >> __all__, automatic import of submodules are disabled (sorry, I don't have >> pointer to specification about this behavior). >> >> For example, some modules depends on email.parser or email.feedparser. >> But since email/__init__.py uses __all__, all submodules >> are imported eagerly. >> >> See >> https://github.com/python/cpython/blob/master/Lib/email/__init__.py#L7-L25 >> >> Changing __all__ will break backward compatibility. >> With __getattr__, this can be lazy import: >> >> import importlib >> >> def __getattr__(name): >> if name in __all__: >> return importlib.import_module("." + name, __name__) >> raise AttributeError(f"module {__name__!r} has no attribute {name!r}") >> >> >> Regards, >> >> _______________________________________________ >> Python-ideas mailing list >> Python-ideas@python.org >> https://mail.python.org/mailman/listinfo/python-ideas >> Code of Conduct: http://python.org/psf/codeofconduct/ >> > > > > -- > --Guido van Rossum (python.org/~guido) _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
