Is it possible to use pyparsing for nested calls in a string?

Question

I'm developing a parser for a config format that also uses functions and I'm trying to figure if it's possible to use pyparsing for this task.

My input is

%upper(%basename(filename)fandsomemore)f%lower(test)f _ %lower(test2)f

and the finite result should be

FILENAMEANDSOMEMOREtest _ test2

In order to do this I first have to get the function names and arguments. My current code works only for the upper function and the nested basename and only if the "andsomemore" part is missing. The code is bellow:

from pyparsing import *

identifier = Word(alphas)
integer  = Word(nums)
functor = identifier
expression = Forward()

lparen = Literal("%").suppress() + functor + Literal("(").suppress()
rparen = Literal(")f").suppress()

argnrec = identifier | integer
arg = Group(expression) | argnrec
args = arg + ZeroOrMore("," + argnrec)
expression << Group(lparen + args + rparen)

print expression.parseString("%upper(%basename(filename)f)f%lower(test)f%lower(test2)f")
print expression.parseString("%upper(%basename(filename)fandsomemore)f%lower(test)f _ %lower(test2)f")

This works great for the first print and outputs, as expected

[['upper', [['basename', 'filename']]]]

For the second print I have an error:

pyparsing.ParseException: Expected ")f" (at char 27), (line:1, col:28)

Is there any way to get this to work with pyparsing? If not, any alternative approach would be appreciated. Also, keep in mind that this must handle more complex arguments, like windows paths (the current code only works for alphas and numbers)

Later update: The purpose for this is to be able to insert the functions anywhere in a string. Another possible usage would be:

 %upper(this)f is a %lower(TEST)f and m%upper(%lower(ORE)f)f

That will result in the end to

THIS is a test and mORE

Answer 1

Just having a play here, I'm not entirely sure what you want but perhaps this will help?

from pyparsing import *

identifier = Word(alphas+nums+'_')
integer  = Word(nums)
functor = identifier
expression = Forward()

lparen = Literal("%").suppress() + functor + Literal("(").suppress()
rparen = Literal(")f").suppress()

term = (lparen + expression + rparen) | identifier
#args = term + ZeroOrMore("," + argnrec)
expression << OneOrMore(term)

print(expression.parseString("%upper(%basename(filename)f)f%lower(test)f%lower(test2)f"))
print(expression.parseString("%upper(%basename(filename)fandsomemore)f%lower(test)f _ %lower(test2)f"))

C:\temp>python test.py
['upper', 'basename', 'filename', 'lower', 'test', 'lower', 'test2']
['upper', 'basename', 'filename', 'andsomemore', 'lower', 'test', '_', 'lower', 'test2']