[Python-Dev] Zip imports, PEP 273, and the .zip extension

[Guido van Rossum]

> PEP 273 does not mandate a particular file extension for zip
> files. However, both current implementations (Jim Ahlstrom's patch and
> Just's import hooks) recognise zip files via the extension ".zip".
> 
> I'd like to suggest that this should not be the case, and that
> zipfiles should be recognised by the embedded signature, as is done by
> zipfile.is_zipfile(). This will (slightly) slow down the initial
> checking for zipfiles, as it requires a file read, but if the result
> of the check is cached the performance impact will be minimal.
> 
> The main advantage of this is in generality. However, I have a
> specific usage in mind - namely, concatenating a Python script with
> its supporting code as a zip archive. (Zip archives can have arbitrary
> data prepended without affecting their validity). Then, simply by
> executing
> 
>     sys.path.append(sys.argv[0])
> 
> the script can access its own embedded modules.
> 
> One problem with getting this to work is that at present, the Python
> parser will choke on data appended to the script. This can be avoided
> under Windows by a system-specific hack, of embedding a ^Z character
> in the script (which text-mode I/O treats as EOF) just before the
> appended data. In the longer term, a language-mandated "stop parsing
> here" token, like Perl's __END__, might be useful. But that's not
> something I'm proposing right now (unless an expert in Python's parser
> steps up and says "oh, that's easy - I can implement that in a couple
> of lines of code" :-))
> 
> Any comments?

-1.  Too much of a hack.

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