Re: [Pyparsing] A newbie w/nested structures

[Paul M. <pa...@al...>]

Tim -

Sorry, I must have mis-pasted the sample, here it is again.  It parses okay
on my system (and I tested versions back to 1.4.2).

from pyparsing import *

LT,GT,EQ,LPAR,RPAR,LBRK,RBRK,BAR,QUOT,SEMI = map(Suppress,"<>=()[]|';")
upper = srange("[A-Z]")
lower = upper.lower()
attrName = Word(lower,alphanums+"_")

key = attrName | (LBRK+quotedString+RBRK)
quotedString.setParseAction(removeQuotes)

valueDef = Forward()
valueDef << ( key + EQ + LT + ZeroOrMore( Group(valueDef | quotedString )) +
GT )
ontologySection = "ontology" + valueDef

comment = "--" + restOfLine
ontologySection.ignore(comment)

sample = """
ontology
	term_definitions = <
		["en"] = <
			items = <
				["at0000"] = <
					description = <"Generic reporting
composition in response to a request for information or testing">
					text = <"Report">
				>
				["at0001"] = <
					description = <"@ internal @">
					text = <"Tree">
				>
				["at0002"] = <
					description = <"Information about
the request">
					text = <"Request details">
				>
				["at0003"] = <
					description = <"Identification of
the request">
					text = <"Request identifier">
				>
			>
		>
	>
"""

res = ontologySection.parseString(sample)
from pprint import pprint
pprint( res.asList() )

This prints:

['ontology',
 'term_definitions',
 ['en',
  ['items',
   ['at0000',
    ['description',
     ['Generic reporting composition in response to a request for
information or testing']],
    ['text', ['Report']]],
   ['at0001', ['description', ['@ internal @']], ['text', ['Tree']]],
   ['at0002',
    ['description', ['Information about the request']],
    ['text', ['Request details']]],
   ['at0003',
    ['description', ['Identification of the request']],
    ['text', ['Request identifier']]]]]]

Your description of key and valueDef are completely correct.  If you want
another example of Forward, I just posted this on comp.lang.python -
http://groups.google.com/group/comp.lang.python/browse_frm/thread/4f128e9df5
4d6962/# - it is a basic nested example with words enclosed in nested
braces.

-- Paul


-----Original Message-----
From: pyp...@li...
[mailto:pyp...@li...] On Behalf Of Tim Cook
Sent: Sunday, September 09, 2007 5:41 AM
To: PyParsing List
Subject: Re: [Pyparsing] A newbie w/nested structures

Hi Paul,

On Sun, 2007-09-09 at 04:30 -0500, Paul McGuire wrote:
> Here are some suggestions on getting started:
> - pick a part of the sample ADL (I would suggest working section by 
> section)
> - develop a simple BNF for this grammar
> 
> Here is a sample parser for the ontology section. 

This is exactly what I started with.  Well, it's what I dropped back to when
I realized how difficult it would be. :-)

>  It is a recursive
> example, defining a valueDef that is defined in terms of component 
> valueDefs.  It also shows the comment format, and the mechanism for 
> skipping comments.  I hope this sample gives you a jump start on a 
> more complete ADL parser.

Thank you so very much for your prompt and informative reply.  


> valueDef = Forward()
> valueDef << ( key + EQ + LT + ZeroOrMore( Group(valueDef | 
> quotedString )) + GT )

I am certain that my problem is that I still do not have a good grasp of
Forward().

Is this the meaning of the valueDef assignment?

"valueDefs are composed of a key followed by an = followed by < and then
zero or more embedded valueDefs or quoted strings. The key is composed of an
attribute name or a bracketed and quoted string"

BTW: The example you sent raises ParseException;
pyparsing.ParseException: Expected ">" (at char 55), (line:4, col:17)

Thanks.
Tim
 


--
Timothy Cook, MSc
Health Informatics Research & Development Services
http://timothywayne.cook.googlepages.com/home
01-904-322-8582