How to get the original text back from a pyparsing token

问题

I have a text of the form name(sum(value1,sum(value2,value3)), "sumname") and pyparsing returns the appropiate tokens, however, I am interested in getting the real text back and I cannot find how.

I have tried setParseAction with a function, but since it only returns string and location, I cannot cope with the trailing part. like, I will only get:

"sum(value2,value3)), "sumname")"
"sum(value1,sum(value2,value3)), "sumname")"
"name(sum(value1,sum(value2,value3)), "sumname")"

And this is not ideal, I do not want to reparse the string manually to get the actual original string.

The way I am trying atm is:

tokens = grammar.parseString(target_string)  
print >>sys.stderr, pyparsing.originalTextFor(tokens)

But this does not really work:

AttributeError: 'NoneType' object has no attribute 'setParseAction'

回答1:

Wrap your expression in the pyparsing helper originalTextFor.

from pyparsing import makeHTMLTags, originalTextFor

sample = '<tag attr1="A1" attr2="B3">'

openTag = makeHTMLTags('tag')[0]

# the expression returned by makeHTMLTags parses the tag and 
# attributes into a list (along with a series of helpful 
# results names)
print (openTag.parseString(sample).asList())

# prints
# ['tag', ['attr1', 'A1'], ['attr2', 'B3'], False]

# wrap in 'originalTextFor' to get back the original source text
print (originalTextFor(openTag).parseString(sample).asList())

# prints
# ['<tag attr1="A1" attr2="B3">']

回答2:

Depending on what you are trying to accomplish by getting the original matching text, you might find better solutions using scanString or transformString:

from pyparsing import makeHTMLTags, replaceWith

sample = '<other><div></div><tag attr1="A1" attr2="B3"><something>'
openTag = makeHTMLTags('tag')[0]

# grammar.scanString is a generator, yielding tokens,start,end tuples
# from the start:end values you can slice the original text from the
# source string
for tokens,start,end in openTag.scanString(sample):
    print tokens.dump()
    print sample[start:end]

# if your goal in getting the original data is to do some kind of string
# replacement, use transformString - here we convert all <TAG> tags to <REPLACE> tags
print openTag.setParseAction(replaceWith("<REPLACE>")).transformString(sample)

prints:

['tag', ['attr1', 'A1'], ['attr2', 'B3'], False]
- attr1: A1
- attr2: B3
- empty: False
- startTag: ['tag', ['attr1', 'A1'], ['attr2', 'B3'], False]
  - attr1: A1
  - attr2: B3
  - empty: False
  - tag: tag
- tag: tag
<tag attr1="A1" attr2="B3">
<other><div></div><REPLACE><something>

来源：https://stackoverflow.com/questions/17395193/how-to-get-the-original-text-back-from-a-pyparsing-token

标签

python

pyparsing