Is this technique acceptable for constructing ParseResults in pyparsing?

I feel that ParseActions make my code a bit clunky when trying to construct the resulting parse tree (known as ParseResults in pyparsing).

What I'm doing now is to have global var开发者_开发知识库iables that store groups of matched tokens that are returned by the Group element. Then at the end, I will inject the results back into the toks dictionary. Is this ok ?

My sketchy grammar:

grammar = ZeroOrMore( Or( ExprA, ExprB, ExprC ) )

Note that ExprA, ExprB etc. can interleave in any order. But I want to group all expressions of one type into one dictionary entry in ParseResults. What do you think of my technique ? I don't like to use global variables because it makes multithreading a problem. Do I have other choices ?

Have you thought about using setResultsName with listAllMatches=True? Here's a demo:

from pyparsing import *

aExpr = Word("A", nums)
bExpr = Word("B", nums)
cExpr = Word("C", nums)

grammar = ZeroOrMore(aExpr.setResultsName("A",listAllMatches=True) |
                     bExpr.setResultsName("B",listAllMatches=True) |
                     cExpr.setResultsName("C",listAllMatches=True) )


results = grammar.parseString("A1 B1 A2 C1 B2 A3")
print results.dump()

prints:

['A1', 'B1', 'A2', 'C1', 'B2', 'A3']
- A: ['A1', 'A2', 'A3']
- B: ['B1', 'B2']
- C: ['C1']

EDIT:

The newer form for this would be:

grammar = ZeroOrMore(aExpr("A*") | bExpr("B*") | cExpr("C*") )

I found ".setResultsName" to be too verbose and cluttering when defining grammars, which worked against my intention of encouraging people to use results names.