[Zope3-dev] Zope 3 needs pyexpat?

[Fred L. Drake, Jr.]

Martijn Faassen writes:
 > Okay, good. And I saw you're checking in at least one change to Zope 3
 > to use the One True Way. I'll go and adjust Zope 2's ParsedXML to try
 > to use this One True Way as well, and someone also needs to fix test.py

I just fixed this in the Zope 2.7 development area as well.

 > People have just not been reading the documentation, I guess. :)

I wish I weren't accustomed to that...

 > If I update this stuff, what's the difference between what I get from
 > 
 > from xml.parsers import pyexpat 
 > 
 > and
 > 
 > from xml.parsers import expat
 > 
 > Is it the same module or are there also differences?

pyexpat and xml.parsers.pyexpat are extension modules.  pyexpat is
provided by Python, and xml.parsers.pyexpat is provided by PyXML.
xml.parsers.expat is a Python module that imports whichever is
available, making everything available from the same module regardless
of which installation variant you're using.

 > Good. Which I import with from "xml.parsers import expat", but it's called
 > pyexpat. Perhaps we should just call it 'expat' and not confuse people by
 > referring to 'pyexpat' lest they decide they should try to import that 
 > (and sometimes this works :).

The name pyexpat is two things:  1) historical baggage, and 2) a good
way for me to refer to the Python bindings when I'm also talking about
the underlying library.  (Others can do this as well. ;)  "pyexpat" is
the Python binding (not the public API), and "Expat" is the C
library.

 > That'll be a tremendous help, however won't completely fix matters if
 > people still do things like:
 > 
 > import pyexpat
 > 
 > or 
 > 
 > from xml.parsers import pyexpat

Those are programmers errors, and will at least break in a meaningful
way when the module doesn't exist.  The difficulty with
xml.parsers.expat is just the usual partial import problem; painful,
but probably not solvable in the general case.

 > Thanks for the explanations! Sorry for my expressions of frustration. :)

Don't be sorry, and don't think you're the only one!  I'm definately
looking forward to Python 2.3, so we can just expect Expat to be
there.


  -Fred

-- 
Fred L. Drake, Jr.  <fdrake at acm.org>
PythonLabs at Zope Corporation