[XML-SIG] Using PyExpat.py

[Don Wakefield]

>>>>> "Uche" == Uche Ogbuji <uche.ogbuji@fourthought.com> writes:

Uche> I do recommend the upgrade, and 0.6.4 is on its way.

I installed 0.6.3, and immediately encountered several problems. Part of
this may be my freshness to Python. My environment may not be complete
in some way. First things first:

 - Using the code supplied by Uche below, I got a complaint of 'os' not
   being visible within PyExpat.py. It isn't imported there, and my
   importing it into my calling script didn't help. I had to add the
   'import os' to the top of PyExpat.py to eliminate this error.

- The next problem was this:

  > python Timediag.py cs39.xml
  Traceback (innermost last):
    File "Timediag.py", line 19, in ?
      x = Cells(sys.argv[1])
    File "Timediag.py", line 11, in __init__
      xml_dom_object = reader.fromUri(filename)
    File "/user/donw/src/local/ss5/obj/lib/python1.5/site-packages/xml/dom/ext/reader/PyExpat.py", line 80, in fromUri
      rt = self.fromStream(stream, doc,stripElements)
    File "/user/donw/src/local/ss5/obj/lib/python1.5/site-packages/xml/dom/ext/reader/PyExpat.py", line 64, in fromStream
      if not self._override:
  AttributeError: _override

  And indeed this variable is not defined in PyExpat.py. I added a line to my own script thusly:

    reader._override = None

  This eliminated that error, allowing me to move on to the next one.

- Here is the next traceback:

  > python Timediag.py cs39.xml
  Traceback (innermost last):
    File "Timediag.py", line 20, in ?
      x = Cells(sys.argv[1])
    File "Timediag.py", line 12, in __init__
      xml_dom_object = reader.fromUri(filename)
    File "/user/donw/src/local/ss5/obj/lib/python1.5/site-packages/xml/dom/ext/reader/PyExpat.py", line 80, in fromUri
      rt = self.fromStream(stream, doc,stripElements)
    File "/user/donw/src/local/ss5/obj/lib/python1.5/site-packages/xml/dom/ext/reader/PyExpat.py", line 65, in fromStream
      self.initParser()
    File "/user/donw/src/local/ss5/obj/lib/python1.5/site-packages/xml/dom/ext/reader/PyExpat.py", line 51, in initParser
      self.parser=pyexpat.ParserCreate()
  NameError: pyexpat

  Based on my experience with 'os', I placed the line 'from xml.parsers import pyexpat'
  directly into PyExpat.py. Now that error has gone away...

- I ran again, and got:

  > python Timediag.py cs39.xml
  Traceback (innermost last):
    File "Timediag.py", line 20, in ?
      x = Cells(sys.argv[1])
    File "Timediag.py", line 12, in __init__
      xml_dom_object = reader.fromUri(filename)
    File "/user/donw/src/local/ss5/obj/lib/python1.5/site-packages/xml/dom/ext/reader/PyExpat.py", line 81, in fromUri
      rt = self.fromStream(stream, doc,stripElements)
    File "/user/donw/src/local/ss5/obj/lib/python1.5/site-packages/xml/dom/ext/reader/PyExpat.py", line 67, in fromStream
      self.initState(doc, stripElements)
  TypeError: too many arguments; expected 2, got 3

  Checking in PyExpat.py, I indeed discovered that the caller was
  supplying stripElements, while the method did not take such an
  argument. I.e.:

  class Reader:
        :
     def initState(self, doc=None):
        :
     def fromStream(self, stream, doc=None, stripElements=None):
        if not self._override:
            self.initParser()
        self.initState(doc, stripElements)

  I've stopped here.

Admittedly some of these problems may stem from my limited understanding
of Python modules and/or namespaces. But the checking of an undefined
variable, and the calling of a method with more than the defined number
of arguments, leads me to believe that I've somehow managed to pick up a
corrupted/scrambled version of PyXML-0.6.3.tar.gz. Is this possible? Or
do 0.6.2 and 0.6.3 just work better with Python 2.0? I'm currently stuck
with 1.5.2, so I hope not.

Uche> As a forewarning, the 0.6.3 and up way is

Uche> from xml.dom.ext.reader import PyExpat     #or Sax2
Uche> reader = PyExpat.Reader()
Uche> xml_dom_object = reader.fromUri(filename)  #should work for either URL or file

By the way, thanks for all the friendly advice so far. I've noticed that
this list has more traffic by far relating to development work than
questions like mine, so I hope this isn't an intrusion.

-- 
Don Wakefield                              Mentor Graphics Corporation
(503) 685-1262                             8005 S.W. Boeckman Road    
don_wakefield@mentorg.com                  Wilsonville, OR 97070-7777