How to get values of a pyparsing parser from parseAction

Question

I have this pyparsing variable in a class:

def takeval(type, name, value):
     #do stuff with args
    
self.variable = pp.Optional(self.let_ | self.const_ | self.var_).set_results_name('vartype') ^ self.varname ^ self.set_ ^ self.object
#I want to set the function

self.variable = self.variable.setParseAction(takeval(vartype, varname, object))

How would I get the values of vartype, varname and object from a parse action?

• I want vartype to be the value of one of: self.let_, self.const_ or self.var_
• I want varname to be the value of self.varname
• I wan object to be the value of self.object

Example of goal output:

I parse the string: 'const hi = "hello"'

I want 'const', 'hi', 'hello' to be sent to the target function.

Any help appreciated!

Answer 1

I have even three versions for you.

• Version 1 needs for each of you parser actions a separate call parser action.
• Verison 2 needs only one such function.
• Version 3 needs nothing of such but the caller code is not so nice any more.

Normally I use the result names a lot. But for simplification I did not do this in this example.

from pyparsing import *

class Parser:
    
  def takeval(self, type, name, value):
    print("Type is " + type)
    print("Name is " + name)
    print("Value is "+ value)
  
  # For version 1
  def call_takeval(self, s, loc, toks):
    self.takeval(toks[0], toks[1], toks[2])
  
  # For version 2
  def as_parse_action(self, parse_action):
    def call_parse_action(s, loc, toks):
      parse_action(toks[0], toks[1], toks[2])
    return call_parse_action
  
  
  def __init__(self):
  
    self.let_ = Literal("let")
    self.const_ = Literal("const")
    self.var_ = Literal("var")
    self.varname = Word(alphas)
    self.set_ = Literal("=")
    self.obj = Literal('"').suppress() + Word(alphas) + Literal('"').suppress()
    
    self.variable_version_1 = Optional(self.let_ | self.const_ | self.var_).setResultsName('vartype') \
        + self.varname.setResultsName('varname') + self.set_.suppress() + self.obj.setResultsName('varobj')
    
    self.variable_version_2 = Optional(self.let_ | self.const_ | self.var_).setResultsName('vartype') \
        + self.varname.setResultsName('varname') + self.set_.suppress() + self.obj.setResultsName('varobj')
    
    self.variable_version_3 = Optional(self.let_ | self.const_ | self.var_).setResultsName('vartype') \
        + self.varname.setResultsName('varname') + self.set_.suppress() + self.obj.setResultsName('varobj')

    self.variable_version_1 = self.variable_version_1.setParseAction(self.call_takeval)
    
    self.variable_version_2 = self.variable_version_2.setParseAction(self.as_parse_action(self.takeval))
    
    self.variable_version_3 = self.variable_version_2.setParseAction( \
        lambda s, loc, toks : self.takeval(toks[0], toks[1], toks[2]))
    
    
    
  def parse(self, text):
    print("Version 1:")
    self.variable_version_1.parseString(text)
    print("Version 2:")
    self.variable_version_2.parseString(text)
    print("Version 3:")
    self.variable_version_3.parseString(text)



test_string = 'const hi = "hello"'
parser = Parser()
parser.parse(test_string)