Best way to represent an outline?

[Dave Kuhlman]

holger krekel wrote:

> VanL wrote:
>> Hello,
>> 
>> I'm trying to figure out the best way to represent an
>> outline, but I'm not sure what to use for each node:
> 
> could you give an example/definition what you mean
> by 'outline'?
> 
>     holger

I'm going to guess a bit about what you mean by an outline.

An outline is a proper tree, i.e. a set of nodes, each of which has 
some content, possibly some attributes, and a set of (possibly 
empty) children.  Every note has exactly one parent node except of 
one (special) node, the root node.

So, one thing to notice is that every XML document satisfies this 
definition.  (And, *no*, I do *not* think that every problem cries 
out for an XML solution. 2%, possibly more, of the world's problems 
can be solved in some other, admittedly less attractive, way.)  
Therefore, (#1) you might try encoding a sample outline as an XML 
document, then read it in using PyXML and minidom, then do your 
processing on the minidom tree.

Or, (#2) you might read the XML document document into minidom, 
then walk that tree and create a tree of nodes, where each node is 
defined by a Python class.  Here is a sample class definition to 
get you started:

# ===========================================

class Node:
    def __init__(self, label='', text='', children=None):
        self.label = label
        self.text = text
        if children is None:
            self.children = []
        else:
            self.children = children
    def show(self, outfile, level):
        self.showLevel(outfile, level)
        outfile.write('%s.  %s\n' % (self.label, self.text))
        for child in self.children:
            child.show(outfile, level + 1)
    def showLevel(self, outfile, level):
        for idx in range(level):
            outfile.write('    ')

# ===========================================

And (#3), if you describe your XML representation of an outline in 
XML Schema, then I have a Python script that will generate the code 
that represents the classes and will parse the XML representation 
and create the tree structure of instances of those classes.  You 
can find generateDS.py along with an outline example at my Web site 
(http://www.rexx.com/~dkuhlman/#generateDS).  You will have to 
install PyXML in order to use it.

Note, that XML is only one way to represent an outline/tree in 
text.  Using XML has the advantage that there are parsers available 
and so part of you work has been done for you.  If we were Lisp 
people, we'd use S-expressions and lots of parentheses.  (Argh! I 
knew I should not have said "Lisp". Now, we've started another "Re: 
Is Python better than X, Was: ..."-war.)

  - Dave


-- 
Dave Kuhlman
dkuhlman at rexx.com
http://www.rexx.com/~dkuhlman