Print a tree of pyparsing result

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 ?

score 5 · Accepted Answer · answered Mar 23 '12 at 18:52

5

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. "

answered Mar 23 '12 at 18:52

David Pointer

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2
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Thanks, i have made something like the SimpleBool – Nine Mar 29 '12 at 22:50
2

Excellent! I'm thinking your implementation looks like a reasonable start. – David Pointer Mar 30 '12 at 20:11
1

exactly what I was looking for! without the tagging it is hard to make sense of the types in the tree. – dashesy Jan 22 '15 at 17:01

score 2 · Answer 2 · answered Mar 29 '12 at 22:58

Prefer to add an answer instead of the edit the question, to much code ..

Isn't perfect, the levels don't get right and the classes could be discarded if I could get the resultsName from printAction. Maybe should create a new question :-/

If someone use it and improve please say how :)

#!/usr/bin/python

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

data = Forward()

level = 0
arrayExpr = Forward()

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

class TreeChild(object):
    def __init__(self,t):
        self.args = t 
    def __str__(self):
        ret = " %s: " % self.name 
        return  ' ' * level + ret + self.args[0] + "\n" 

class TreeBranch(object):
    def __init__(self,t):
        self.args = t 
    def __str__(self):
        global level 
        level = level + 1
        childs = " ".join(map(str,self.args))
        level = level - 1
        ret = " %s: " % self.name + '\n'
        return  ' ' * level + ret + childs + "\n"

class Frame(TreeBranch):
    name = 'frame'

class Char(TreeChild):
    name = 'char'

class Boolean(TreeChild):
    name = 'boolean'

class Id(TreeChild):
    name = 'id'

class Array(TreeBranch):
    name = 'array'

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

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

frame = (Word(hexnums, exact=2)('id').setParseAction(Id) \
    + data('data'))('frame').setParseAction(Frame)

result = frame.parseString("020103030104020302");
print result[0]

Print a tree of pyparsing result

2 Answers2