PEP: import version

[Manlio Perillo]

On Thu, 13 May 2004 18:07:27 +1000, Andrew Bennetts
<andrew-pythonlist at puzzling.org> wrote:

>On Thu, May 13, 2004 at 07:46:51AM +0000, Manlio Perillo wrote:
>[...]
>> A possible syntax is this:
>> import wxPython version '2.4'
>
>I'd like to see versioned imports too, but it looks like a tricky problem to
>me.  Some questions that immediately spring to mind reading your proposal:
>
>How would this work with from X import Y?  How would this work with packages
>(e.g. import X.Y.Z)?
>
>e.g. how would you add version requirements to these statements:
>
>    from gtk import main
>

I see a simple solution:
from gtk version '2.0' import main

It should be up to gtk root module (ex __init__.py) to decide what
version of sub modules to load.



>But what about the second one -- can only top-level modules/packages have
>versions?  e.g. what if the "twisted.web" package has a version that's
>independent of the top-level "twisted" container package?  Would "from
>twisted.web version '1.3.0'" mean Twisted version 1.3.0, or Twisted Web
>version 1.3.0?
>

The sub-level packages have version too.
In example:

twisted version 1.3.0 -> web version 1.1
twisted version 1.3.5 -> web version 1.1
twisted version 1.4.0 -> vew version 1.2

The right sub module version to load is decided by the top level
module.

In detail (using a single file for all versions):
__init__.py

if __version__ == '1.4.0':
	__all__  = [ ('web', '1.2'),
	                      ...
		 ]
elif __version__ == '1.3.5':
	_all =  [ ('web', '1.1'),
	              ...
	            ]

That is, the items of __all__ should be tuples.

>What happens if the same program tries to import different (and possibly
>conflicting) versions of the same module, e.g.:
>
>    import gtk version '2.0'
>    import gtk version '1.2'
>

>Should an ImportError be raised?  Should it succeed (assuming both versions
>are available)?  Is it even possible to have two different versions of the
>same library/module installed in parallel, and if so, how?

It should unload gtk version 2.0 and load the version 1.0



Regards   Manlio Perillo