handy stacktrace class

[Will Ware]

I was fooling with some Python code, and starting to miss the
Exception.printStackTrace() feature in Java. Here is a stab at
something roughly analogous, which puts together a stacktrace
as an XML document.

import xml.dom.minidom

class Stacktrace(xml.dom.minidom.Document):
    def __init__(self):
        import sys
        xml.dom.minidom.Document.__init__(self)
        stacktrace = self.createElement("stacktrace")
        self.appendChild(stacktrace)
        try:
            raise Exception
        except:
            tb = sys.exc_traceback
        x = tb.tb_frame.f_back
        while x != None:
            f = x.f_code
            frame = self.createElement("frame")
            frame.setAttribute("func", f.co_name)
            frame.setAttribute("file", f.co_filename)
            frame.setAttribute("line", repr(f.co_firstlineno))
            stacktrace.appendChild(frame)
            x = x.f_back
    def __repr__(self):
        import xml.dom.ext
        class MyStream:
            def __init__(self):
                self.str = ""
            def write(self, x):
                self.str += x
        stream = MyStream()
        xml.dom.ext.PrettyPrint(self, stream)
        return stream.str[:-1]   # trim trailing newline

The rational for doing this as an XML document was, uh, gee, I
thought I had a good reason at the time. I think I've seen XML
sequences of stacktraces elsewhere and it looked like a good idea.
My brief time of muddling about with xml.dom.minidom makes me
think that elements are inherently tied to a particular document
and can't just be lifted and moved to another document, as one
might want to do to, say, build a sequence of stacktraces while
debugging something. But I'm sure there's some kind of workaround
for that.