[Pyobjc-dev] Re: [Python-Dev] The meaning of __all__

[Guido v. R. <gu...@py...>]

> There's a discussion over on the pyobjc developers mailing list at the 
> moment about the use of __all__.
> 
> Some people suggested that for a certain module we only put "often 
> used" items in __all__, so that "from module import *" will import only 
> these commonly used items into your namespace. The module would contain 
> other items which *are* useful and which should be callable from the 
> outside, but these would have to be explicitly imported into your 
> namespace (or used via "import objc; objc.SetVerbose()".
> 
> This doesn't feel right to me, as I've always used __all__ to mean "the 
> whole externally visible API", and I've considered anything else that 
> the module exports basically an artefact of the implementation. But 
> when I looked this up in the reference manual it is rather vague about 
> this.
> 
> Any opinions on the matter?

__all__ should contain the entire public API.  It's mostly intended to
avoid accidentally exporting other things you've *imported* like os,
sys, and other library modules.  Another way of doing that would be
to write e.g.

  import sys as _sys

but I don't like excessive underscoring.

--Guido van Rossum (home page: http://www.python.org/~guido/)