[Python-ideas] PEP 562
INADA Naoki
songofacandy at gmail.com
Sun Sep 10 23:08:12 EDT 2017
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,
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