Question

I’m suppose to capture everything inside a tag and the next lines after it, but it’s suppose to stop the next time it meets a bracket. What am i doing wrong?

import re #regex

regex = re.compile(r"""
         ^                    # Must start in a newline first
         \[\b(.*)\b\]         # Get what's enclosed in brackets 
         \n                   # only capture bracket if a newline is next
         (\b(?:.|\s)*(?!\[))  # should read: anyword that doesn't precede a bracket
       """, re.MULTILINE | re.VERBOSE)

haystack = """
[tab1]
this is captured
but this is suppose to be captured too!
@[this should be taken though as this is in the content]

[tab2]
help me
write a better RE
"""
m = regex.findall(haystack)
print m

what im trying to get is:
[(‘tab1’, ‘this is captured\nbut this is suppose to be captured too!\n@[this should be taken though as this is in the content]\n’, ‘[tab2]’,’help me\nwrite a better RE\n’)]

edit:

regex = re.compile(r"""
             ^           # Must start in a newline first
             \[(.*?)\]   # Get what's enclosed in brackets 
             \n          # only capture bracket if a newline is next
             ([^\[]*)    # stop reading at opening bracket
        """, re.MULTILINE | re.VERBOSE)

this seems to work but it’s also trimming the brackets inside the content.

Answer 1

Python regex doesn’t support recursion afaik.

EDIT: but in your case this would work:

regex = re.compile(r"""
         ^           # Must start in a newline first
         \[(.*?)\]   # Get what's enclosed in brackets 
         \n          # only capture bracket if a newline is next
         ([^\[]*)    # stop reading at opening bracket
    """, re.MULTILINE | re.VERBOSE)

EDIT 2: yes, it doesn’t work properly.

import re

regex = re.compile(r"""
    (?:^|\n)\[             # tag's opening bracket  
        ([^\]\n]*)         # 1. text between brackets
    \]\n                   # tag's closing bracket
    (.*?)                  # 2. text between the tags
    (?=\n\[[^\]\n]*\]\n|$) # until tag or end of string but don't consume it
    """, re.DOTALL | re.VERBOSE)

haystack = """[tag1]
this is captured [not a tag[
but this is suppose to be captured too!
[another non-tag

[tag2]
help me
write a better RE[[[]
"""

print regex.findall(haystack)

I do agree with viraptor though. Regex are cool but you can’t check your file for errors with them. A hybrid perhaps? 😛

tag_re = re.compile(r'^\[([^\]\n]*)\]$', re.MULTILINE)
tags = list(tag_re.finditer(haystack))

result = {}
for (mo1, mo2) in zip(tags[:-1], tags[1:]):
    result[mo1.group(1)] = haystack[mo1.end(1)+1:mo2.start(1)-1].strip()
result[mo2.group(1)] = haystack[mo2.end(1)+1:].strip()

print result

EDIT 3: That’s because ^ character means negative match only inside [^squarebrackets]. Everywhere else it means string start (or line start with re.MULTILINE). There’s no good way for negative string matching in regex, only character.