Question

I am using pyparsing to parse a hex string and I am searching for an automatic way of print the parser tree.

A near approach is command dump but it print a lot of duplicated info.

For example:

from pyparsing import * #Word, Optional, OneOrMore, Group, ParseException

data = Forward()

arrayExpr = Forward()

def data_array(s,l,t):
    n = int(t[0], 16)
    arrayExpr << ( n * data)
    return t[0]

array = Word(hexnums, exact=2).setParseAction(data_array) + arrayExpr

data << (Literal('01') + array.setResultsName('array')
    | Literal('03') + Word(hexnums, exact=2)('char')
    | Literal('04') + Word(hexnums, exact=2)('boolean'))

frame = (Word(hexnums, exact=2)('id') \
    + data('data'))('frame')

result = frame.parseString("02010203010302");
print result.dump()

The goal is that result of result.dump() was something similar to

 - frame: ['02', '01', '03', '03', '01', '04', '02', '03', '02']
  - id: 02
  - array: ['03', '03', '01', '04', '02', '03', '02']
     - char: 01
     - boolean: 02
     - char: 02

The pretty print isn’t mandatory, the pretended is the tree structure.

Is there a way of make this print or I will need to had a setParseAction for all rules ?

Answer 1

Looks like you’ll need a setParseAction for each of the rules.

From parsing to object hierarchy: “Attach parse actions to each expression, but here is the trick: use a class instead of a function. The class’s init method will get called, and return an instance of that class. “