CODEWITHSUNDEEP
pythonregexstring
alvas
alvas

Reputation: 122012

Recursively capture patterns in regex - Python

Given the solution in How do i extract a list of elements encased in quotation marks bounded by <> and delimited by commas - python, regex?, I was able to capture the prefix and the values of the desired pattern denoted by a CAPITALIZED.PREFIX and values within angle brackets < "value1" , "value2", ... >

"""calf_n1 := n_-_c_le & n_-_pn_le &\n [ ORTH.FOO < "cali.ber,kl", 'calf' , "done" >,\nLKEYS.KEYREL.PRED "_calf_n_1_rel",\n ORHT2BAR <"what so ever >", "this that mess < up"> ,\n LKEYS.KEYREL.CARG "<20>",\nLOOSE.SCREW ">20 but <30"\n JOKE <'whatthe ', "what" >,\n THIS + ]."""

However I get into problems with i have strings like the one above. The desired output would be:

('ORTH.FOO', ['cali.ber,kl','calf','done'])
('ORHT2BAR', ['what so ever >', 'this that mess < up'])
('JOKE', ['whathe ', 'what'])

I have tried the following but it only give me the 1st tuple, how do i get all possible tuples as in the desired output?:

import re
intext = """calf_n1 := n_-_c_le & n_-_pn_le &\n [ ORTH.FOO < "cali.ber,kl", 'calf' , "done" >,\nLKEYS.KEYREL.PRED "_calf_n_1_rel",\n ORHT2BAR <"what so ever >", "this that mess < up">\n LKEYS.KEYREL.CARG "<20>",\nLOOSE.SCREW ">20 but <30" ]."""
pattern = re.compile(r'.*?([A-Z0-9\.]*) < ([^>]*) >.*', flags=re.DOTALL)
f, v = pattern.match(intext).groups()
names = re.findall('[\'"](.*?)["\']', v)
print f, names

Upvotes: 0

Views: 4018

Answers (2)

Jerry
Jerry

Reputation: 71538

Huh silly me. Somehow, I wasn't testing the whole string on my machine ^^;

Anyway, I used this regex and it works, you just get the results you were looking for in a list, which I guess is okay. I'm not too good in python, and don't know how to transform this list into array or tuple:

>>> import re
>>> intext = """calf_n1 := n_-_c_le & n_-_pn_le &\n [ ORTH.FOO < "cali.ber,kl", 'calf' , "done" >,\nLKEYS.KEYREL.PRED "_calf_n_1_rel",\n ORHT2BAR <"what so ever >", "this that mess < up"> ,\n LKEYS.KEYREL.CARG "<20>",\nLOOSE.SCREW ">20 but <30"\n JOKE <'whatthe ', "what" >,\n THIS + ]."""
>>> results = re.findall('\\n .*?([A-Z0-9\.]*) < *((?:[^>\n]|>")*) *>.*?(?:\\n|$)', intext)
>>> print results
[('ORTH.FOO', '"cali.ber,kl", \'calf\', "done"'), ('ORHT2BAR', '"what so ever>", "this that mess < up"'), ('JOKE', '\'whatthe \', "what" ')]

The parentheses indicate the first level elements and the single quotes the second level elements.

Upvotes: 1

Martijn Pieters
Martijn Pieters

Reputation: 1121446

Regular expressions do not support 'recursive' parsing. Process the group between the < and > characters after capturing it with a regular expression.

The shlex module would do nicely here to parse your quoted strings:

import shlex
import re

intext = """calf_n1 := n_-_c_le & n_-_pn_le &\n [ ORTH.FOO < "cali.ber,kl", 'calf' , "done" >,\nLKEYS.KEYREL.PRED "_calf_n_1_rel",\n ORHT2BAR <"what so ever >", "this that mess < up">\n LKEYS.KEYREL.CARG "<20>",\nLOOSE.SCREW ">20 but <30" ]."""
pattern = re.compile(r'.*?([A-Z0-9\.]*) < ([^>]*) >.*', flags=re.DOTALL)
f, v = pattern.match(intext).groups()

parser = shlex.shlex(v, posix=True)
parser.whitespace += ','
names = list(parser)

print f, names

output:

ORTH.FOO ['cali.ber,kl', 'calf', 'done']

Upvotes: 1

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