[Python-Dev] Another approach for the import mechanism

[Brian Quinlan]

Greg Ewing wrote:
> > When the import hook returns a stream, every stream hook is given a
> > chance to transform that stream.  If a stream hook returns a
transformed
> > stream then every other hook is called again. This continues until
no
> > stream hook is interested in transforming the stream anymore.
> 
> How is a stream hook to know what kind of stream it's
> been given?

It will have to figure it out itself, given the original arguments to
the import hook plus the stream itself.

A zip hook might, for example, check that the first 4 bytes of the
stream are 0x04034b50. If they aren't, it would have to repair the
original stream (haven't really thought about how to do this) and signal
its lack of interest. Otherwise it would open the archive, decompress it
and return a new stream. 

The more I think about this mechanism, the fewer interesting problems it
seems to solve.

Maybe the real answer is to have a single import hook but write as much
of it as possible in modular Python. Then the user can figure out how to
manage the competing interests when importing archived, encrypted
modules from an arbitrary URL.

Cheers,
Brian