Regex to match special list items II

Question

I have weird list of items and lists like this with | as a delimiters and {{ }} as a parenthesis. It looks like this:

| item1 | item2 | item3 | {{Ulist1 | item4 | item5 | {{Ulist2 | item6 | item7 }} | item8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item14

I want to match items in lists called Ulist* (items 4-8) using RegEx and replace them with Uitem*. The result should look like this:

| item1 | item2 | item3 | {{Ulist1 | Uitem4 | Uitem5 | {{Ulist2 | Uitem6 | Uitem7 }} | Uitem8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item14

Update:

I tried a solution according to this question, but the answer from that question doesn't work, if there is a list inside of an Ulist. It is in Python 2.7, specifically my code is:

#!/usr/bin/python
# -*- coding: utf-8  -*-
import regex
def repl(m):
    return "".join([x.replace("item", "Uitem") if x.startswith("{{Ulist") else x for x in regex.split(r'\{{2}(?=(\blist\d*))[^\}]*(?:}(?!})[^\}]*)*}}', m.group(0))])
text = "| item1 | item2 | item3 | {{Ulist1 | item4 | item5 | {{Ulist2 | item6 | item7 }} | item8 | {{list4 | item15 | item16 }} | item17 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item14"
rex = r'(\{\{(?=(Ulist\d*))(?>[^}{]|}(?!})|\{(?!\{)|(?1))*}})'
text = regex.sub(rex, repl, text)
print(text)

You might find it easier to use something other than regex... it doesn't typically do well with arbitrarily-nested structures. — glibdud, Jan 21 '16 at 13:29
I think so too, but I don't know how. Somebody have already answered this question with some links, how to do it programatically without regex, but he deleted his answer :/ — aleskva, Jan 21 '16 at 13:32
@AlexKupil As I can see this deleted answer, [here's the link](http://stackoverflow.com/questions/546433/regular-expression-to-match-outer-brackets) you're talking about, if it can help. — zessx, Jan 21 '16 at 13:34
I still need a little bit of regex for replacing item to Uitem (because this is just simplified case of what I really want), but the main part of my question (to find Ulists and process items inside) is still openned — aleskva, Jan 21 '16 at 13:36
But still I will be glad if somebody helps me with that. I'll try to make a draw of a code, but I think it will not be working. — aleskva, Jan 21 '16 at 13:45
There we go [again](http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags#answer-1732454). These sort of problems are not suited for regex. Regex is only suited for regular grammars (hence the name). NOT for context sensitive grammars like the one you have. — RickyA, Jan 21 '16 at 14:04
With [Python regex package](https://pypi.python.org/pypi/regex) you could probably [match nested](https://regex101.com/r/dS6wD0/1): `{{Ulist\d+(?>[^}{]+(?0)?)*}}` and [use a callback](http://stackoverflow.com/a/2095012/5527985) on `group(0)` with sub [like this](https://regex101.com/r/wN7qT4/1): `\w[^}{|]+(?<=\w)` — bobble bubble, Jan 21 '16 at 14:10
Finally I tried @glibdud answer and it worked without any problem. Your regex still can't handle list inside Ulist — aleskva, Jan 21 '16 at 21:35

score 2 · Accepted Answer · answered Jan 21 '16 at 13:56

Maybe this can get you started:

def parse(data):
    items = [i.strip() for i in data.split('|')]
    newitems = []
    nest = [False]
    for item in items:
        if item.startswith('{{'):
            if item.startswith('{{Ulist'):
                nest.append(True)
            else:
                nest.append(False)
            newitems.append(item)
        else:
            if item.startswith('item') and nest[-1]:
                newitems.append('U' + item)
            else:
                newitems.append(item)
        if item.endswith('}}'):
            nest.pop()
    return ' | '.join(newitems)

Basically it splits the data on the delimiters (|) and does a single loop over them, converting where appropriate and keeping state in a stack called nest to determine when it should be converting. It assumes that whitespace surrounding delimiters isn't significant.

Yes, no regex here! Therefore a proper answer. – RickyA Jan 21 '16 at 14:05 — RickyA, Jan 21 '16 at 14:05

score 0 · Answer 2 · edited May 23 '17 at 12:23

In fact regex is wrong tool to match parentheses/braces/brackets, see here.

Anyway you can use regex in this case as below-

import regex

s='| item1 | item2 | item3 | {{Ulist1 | item4 | item5 | {{Ulist2 | item6 | item7 }} | item8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1| item1 | item2 | item3 | {{Ulist1 | item4 | item5 | {{Ulist2 | item6 | item7 }} | item8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1| item1 | item2 | item3 | {{Ulist1 | item4 | item5 | {{Ulist2 | item6 | item7 }} | item8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1| item1 | item2 | item3 | {{Ulist1 | item4 | item5 | {{Ulist2 | item6 | item7 }} | item8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1| item1 | item2 | item3 | {{Ulist1 | item4 | item5 | {{Ulist2 | item6 | item7 }} | item8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1| item1 | item2 | item3 | {{Ulist1 | item4 | item5 | {{Ulist2 | item6 | item7 }} | item8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1| item1 | item2 | item3 | {{Ulist1 | item4 | item5 | {{Ulist2 | item6 | item7 }} | item8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1| item1 | item2 | item3 | {{Ulist1 | item4 | item5 | {{Ulist2 | item6 | item7 }} | item8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1'

def itm_changer(txt):
  return ''.join(txt.captures()).replace('item','Uitem')

def changer(data):
  return regex.sub(r'\{\{Ulist\d{0,}(?>[^\}\{]+|(?0))+\}}',lambda x: itm_changer(x),data)

print changer(s)

N.B. You can modify the as you want.

Output-

| item1 | item2 | item3 | {{Ulist1 | Uitem4 | Uitem5 | {{Ulist2 | Uitem6 | Uitem7 }} | Uitem8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1| item1 | item2 | item3 | {{Ulist1 | Uitem4 | Uitem5 | {{Ulist2 | Uitem6 | Uitem7 }} | Uitem8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1| item1 | item2 | item3 | {{Ulist1 | Uitem4 | Uitem5 | {{Ulist2 | Uitem6 | Uitem7 }} | Uitem8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1| item1 | item2 | item3 | {{Ulist1 | Uitem4 | Uitem5 | {{Ulist2 | Uitem6 | Uitem7 }} | Uitem8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1| item1 | item2 | item3 | {{Ulist1 | Uitem4 | Uitem5 | {{Ulist2 | Uitem6 | Uitem7 }} | Uitem8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1| item1 | item2 | item3 | {{Ulist1 | Uitem4 | Uitem5 | {{Ulist2 | Uitem6 | Uitem7 }} | Uitem8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1| item1 | item2 | item3 | {{Ulist1 | Uitem4 | Uitem5 | {{Ulist2 | Uitem6 | Uitem7 }} | Uitem8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1| item1 | item2 | item3 | {{Ulist1 | Uitem4 | Uitem5 | {{Ulist2 | Uitem6 | Uitem7 }} | Uitem8 }} | item9 | {{list3 | item10 | item11 | item12 }} | item13 | item1

To see details of the regex used here SEE LIVE DEMO

Regex to match special list items II

2 Answers2

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