[Distutils] Using Wheel with zipimport

[Nick Coghlan]

On 29 January 2014 22:57, Donald Stufft <donald at stufft.io> wrote:
> Also to be specific, what I believe should be done is that the change should be
> reverted, and if it is desired that Wheels officially support zip import then in the
> next version of the Wheel spec it should be added when everyone has a chance
> to properly discuss it.

Whether you like it or not, the wheel spec *does* already support
being used that way, and changing it *would* be a backwards
incompatible change to the format (and hence not acceptable without a
compelling justification, and there isn't one that wouldn't equally
well apply to other powerful but potentially confusing features like
metaclasses and monkeypatching).

I am also not willing to allow the perception that the wheel format
does not offer a strict superset of the feature of the egg format to
persist until we have a defined wheel 1.1 spec (which we don't even
have a volunteer to work on yet).

So, rather than removing it, I have instead updated the note in PEP 427 to read:

=============================
Is it possible to import Python code directly from a wheel file?
    Yes, the wheel format is deliberately designed to be compatible with
    Python's support for importing from zip files, ensuring that it
    provides a superset of the functionality provided by the preceding
    egg format.

    However, this is generally not a *recommended* approach to using wheel
    files, as importing from a zip file rather than an ordinary filesystem
    directory imposes a number of additional constraints that will often
    break the assumptions of Python developers (for example, C extensions
    cannot be imported directly from a zip archive, and the ``__file__``
    attribute no longer refers to an ordinary filesystem path, but to
    a combination path that includes both the location of the zip archive
    on the filesystem and the relative path to the module inside the
    archive).

    Like metaclasses and metapath importers, if you're not sure if you need
    to take advantage of this feature, you almost certainly don't need it.
=============================

Regards,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia