I am trying to pull a certain number from various strings. The number has to be standalone, before ', or before (. The regex I came up with was:
\b(?<!\()(x)\b(,|\(|'|$) <- x is the numeric number.
If x is 2, this pulls the following string (almost) fine, except it also pulls 2'abd'. Any advice what I did wrong here?
2(2'Abf',3),212,2'abc',2(1,2'abd',3)
Your actual question is, as I understand it, get these specific number except those in parenthesis.
To do so I suggest using the skip_what_to_avoid|what_i_want pattern like this:
(\((?>[^()\\]++|\\.|(?1))*+\))
|\b(2)(?=\b(?:,|\(|'|$))
The idea here is to completely disregard the overall matches (and there first group use for the recursive pattern to capture everything between parenthesis: (\((?>[^()\\]++|\\.|(?1))*+\))): that's the trash bin. Instead, we only need to check capture group $2, which, when set, contains the asterisks outside of comments.
Demo
Sample Code:
import regex as re
regex = r"(\((?>[^()\\]++|\\.|(?1))*+\))|\b(2)(?=\b(?:,|\(|'|$))"
test_str = "2(2'Abf',3),212,2'abc',2(1,2'abd',3)"
matches = re.finditer(regex, test_str, re.MULTILINE)
for matchNum, match in enumerate(matches):
matchNum = matchNum + 1
if match.groups()[1] is not None:
print ("Found at {start}-{end}: {group}".format(start = match.start(2), end = match.end(2), group = match.group(2)))
Output:
Found at 0-1: 2
Found at 16-17: 2
Found at 23-24: 2
This solution requires the alternative Python regex package.
Related
I am trying to write a regex code to find all examples of any character that surrounds one of any character including itself in the string below:
b9fgh9f1;2w;111b2b35hw3w3ww55
So ‘b2b’ and ‘111’ would be valid, but ‘3ww5’ would not be.
Could someone please help me out here?
Thanks,
Nikhil
You can use this regex which will match three characters where first and third are same using back reference, where as middle can be any,
(.).\1
Demo
Edit:
Above regex will only give you non-overlapping matches but as you want to get all matches that are even overlapping, you can use this positive look ahead based regex which doesn't consume the next two characters instead groups them in group2 so for your desired output, you can append characters from group1 and group2.
(.)(?=(.\1))
Demo with overlapping matches
Here is a Java code (I've never programmed in Ruby) demonstrating the code and the same logic you can write in your fav programming language.
String s = "b9fgh9f1;2w;111b2b35hw3w3ww55";
Pattern p = Pattern.compile("(.)(?=(.\\1))");
Matcher m = p.matcher(s);
while(m.find()) {
System.out.println(m.group(1) + m.group(2));
}
Prints all your intended matches,
111
b2b
w3w
3w3
w3w
Also, here is a Python code that may help if you know Python,
import re
s = 'b9fgh9f1;2w;111b2b35hw3w3ww55'
matches = re.findall(r'(.)(?=(.\1))',s)
for m in re.findall(r'(.)(?=(.\1))',s):
print(m[0]+m[1])
Prints all your expected matches,
111
b2b
w3w
3w3
w3w
My input is of this format: (xxx)yyyy(zz)(eee)fff where {x,y,z,e,f} are all numbers. But fff is optional though.
Input: x = (123)4567(89)(660)
Expected output: Only the eeepart i.e. the number inside 3rd "()" i.e. 660 in my example.
I am able to achieve this so far:
re.search("\((\d*)\)", x).group()
Output: (123)
Expected: (660)
I am surely missing something fundamental. Please advise.
Edit 1: Just added fff to the input data format.
You could find all those matches that have round braces (), and print the third match with findall
import re
n = "(123)4567(89)(660)999"
r = re.findall("\(\d*\)", n)
print(r[2])
Output:
(660)
The (eee) part is identical to the (xxx) part in your regex. If you don't provide an anchor, or some sequencing requirement, then an unanchored search will match the first thing it finds, which is (xxx) in your case.
If you know the (eee) always appears at the end of the string, you could append an "at-end" anchor ($) to force the match at the end. Or perhaps you could append a following character, like a space or comma or something.
Otherwise, you might do well to match the other parts of the pattern and not capture them:
pattern = r'[0-9()]{13}\((\d{3})\)'
If you want to get the third group of numbers in brackets, you need to skip the first two groups which you can do with a repeating non-capturing group which looks for a set of digits enclosed in () followed by some number of non ( characters:
x = '(123)4567(89)(660)'
print(re.search("(?:\(\d+\)[^(]*){2}(\(\d+\))", x).group(1))
Output:
(660)
Demo on rextester
I'd like to duplicate a multiple matches in a line, substituting part of the match, but keeping the runs of matches together (that seems to be the tricky part).
e.g.:
Regex:
(x(\d)(,)?)
Replacement:
X$2,O$2$3
Input:
x1,x2,Z3,x4,Z5,x6
Output: (repeated groups broken apart)
X1,O1,X2,O2,Z3,X4,O4,Z5,X6,O6
Desired output (repeated groups, "X1,X2" kept together):
X1,X2,O1,O2,Z3,X4,O4,Z5,X6,O6
Demo: https://regex101.com/r/gH9tL9/1
Is this possible with regex or do I need to use something else?
Update: Wills answer is what I expected. It occurs to me that it might be possible with multiple passes of regex.
You would have to capture the repeating patterns as one match and write out replacements for the whole repeating pattern at once. your current pattern cannot tell that your first and second matches, x1, and x2, respectively, are adjacent.
Im going to say no, this is not possible with one pure regex.
This is because of two important facts about capture groups and replacing.
Repeated capture groups will return the last capture:
Regex's are able to capture patterns which repeat an arbitrary amount of time by using the form <PATTERN>{1,},<PATTERN>+ or <PATTERN>*. However any capture group within <PATTERN> would only return the captures from the last iteration of the pattern. This would prevent your desired ability to capture matches that arbitrarily repeat.
"Hold on", you might say, "I only want to capture patterns that repeat one or two times, I could use (x(\d)(,)?)(x(\d)(,)?)?", which brings us to point 2.
There is no conditional replacement
Using the above pattern we could get your desired output for the repeated match, but not without mangling the solo match replacement.
See: https://regex101.com/r/gH9tL9/2 Without the ability to turn off sections of the replacement based on the existence of capture groups, we cannot achieve the desired output.
But "No, you can't do that" is a challenge to a hacker, I hope I am shown up by a true regex ninja.
Solution with 2 regexes and some code
There's definitely ways to achieve this goal with some code.
Here's a quick and dirty python hack using two regexes http://pythonfiddle.com/wip-soln-for-so-q/
This makes use of python's re.sub(), which can pass matches to one regex to a function ordered_repl which returns the replacement string. By using your original regex within the ordered_repl we can extract the information we want and get the right order by buffering our lists of Xs and Os.
import re
input_string="x1,x2,Z3,x4,Z5,x6"
re1 = re.compile("(?:x\d,?)+") # captures the general thing you want to match using a repeating non-capturing group
re2 = re.compile("(x(\d)(,)?)") # your actual matcher
def ordered_repl(m): # m is a matchobj
buf1 = []
buf2 = []
cap_iter = re.finditer(re2,m.group(0)) # returns an iterator of MatchObjects for all non-overlapping matches
for cap_group in cap_iter:
capture = cap_group.group(2) # capture the digit
buf1.append("X%s" % capture) # buffer X's of this submatch group
buf2.append("O%s" % capture) # buffer O's of this submatch group
return "%s,%s," % (",".join(buf1),",".join(buf2)) # concatenate the buffers and return
print re.sub(re1,ordered_repl,input_string).rstrip(',') # searches string for matches to re1 and passes them to the ordered_repl function
In my specific case I'm using powershell, so I was able to come up with the following:
(linebreaks added for readability)
("x1,x2,z3,x4,z5,x6"
-split '((?<=x\d),(?!x)|(?<!x\d),(?=x))'
| Foreach-Object {
if ($_ -match 'x') {
$_ + ',' + ($_ -replace 'x','y')
} else {$_}
}
) -join ''
Outputs:
x1,x2,y1,y2,z3,x4,y4,z5,x6,y6
Where:
-split '((?<=x\d),(?!x)|(?<!x\d),(?=x))'
breaks apart the string into these groups:
x1,x2
,
z3
,
x4
,
z5
,
x6
using positive and negative lookahead and lookbehind:
comma with x\d before and without x after:
(?<=x\d),(?!x)
comma without x\d before and with x after:
(?<!x\d),(?=x)
with open(searchfile) as f:
pattern = "\.?(?P<sentence>.*?\(([A-Za-z0-9_]+)\).*?)\."
for line in f:
match = re.search(pattern, line)
if match != None:
print match.group("sentence")
I am trying to extract every sentence that contains an acronym in parenthesis (essentially 2-4 letter all caps in parenthesis.
In: Here is an (ABC) example. Do not include this sentence. Include this (AB) one. And (AVCD) this one.
Out: Here is an (ABC) example. Include this (AB) one. And (AVCD) this one.
You can use this:
[^.]*?\([A-Z]{2,4}\)[^.]*\.
But note that it is a particulary inefficient way, since the pattern starts with a very permissive subpattern. You can correct that a little by adding a kind of anchor at the begining:
(?:(?<=.)|^)[^.]*?\([A-Z]{2,4}\)[^.]*\.
Unfortunatly, even with this anchor, the regex engine must check the two alternatives for the most of the characters of the string.
A better approach might be to find substrings starting with the acronym until the end of the sentence and dots, and then to extract substrings using the end offset of each results:
#!/usr/bin/python
import re
txt = 'Here is an (ABC) example. Do not include this sentence. Include this (AB) one. And (AVCD) this one.'
pattern = re.compile(r'([!.?])(?=\s)|\([A-Z]{2,4}\)[^.]*(?:\.|$)')
offset = 0
result = ''
for m in pattern.finditer(txt):
if (m.group(1)==None):
result += txt[offset:m.end()]
offset = m.end()
print result
Note: you can be sure that a dot stands for the end of a sentence, it can be something else.
a little more efficient pattern
([^.(]++\([^.)]++\)[^.)]++\.)
Demo
Python3.3, OS X 7.5
I am attempting to locate all instances of a 4-character substring defined as follows:
First character = 'N'
Second character = Anything but 'P'
Third character = 'S' or 'T'
Fourth character = Anything but 'P'
My query looks like this:
re.findall(r"\N[A-OQ-Z][ST][A-OQ-Z]", text)
This is working except in one particular case where two substrings overlap. That case involves the following 5character substring:
'...NNTSY...'
The query catches the first 4-character substring ('NNTS'), but not the second 4-character substring ('NTSY').
This is my first attempt at regular expressions, and obviously I'm missing something.
You can do this if the re engine does not consume characters as it matches them, which is possible with lookahead assertions:
import re
text = '...NNTSY...'
for m in re.findall(r'(?=(N[A-OQ-Z][ST][A-OQ-Z]))', text):
print(m)
Output:
NNTS
NTSY
Having everything within the assertion works but also feels weird. Another way is taking the N out of the assertion:
for m in re.findall(r'(N(?=([A-OQ-Z][ST][A-OQ-Z])))', text):
print(''.join(m))
From the Python 3 documentation (emphasis added):
$ python3 -c 'import re; help(re.findall)'
Help on function findall in module re:
findall(pattern, string, flags=0)
Return a list of all non-overlapping matches in the string.
If one or more capturing groups are present in the pattern, return
a list of groups; this will be a list of tuples if the pattern
has more than one group.
Empty matches are included in the result.
If you want overlapping instances, use regex.search() in a loop. You have to compile the regular expression because the API for non-compiled regular expressions doesn't take a parameter to specify the starting position.
def findall_overlapping(pattern, string, flags=0):
"""Find all matches, even ones that overlap."""
regex = re.compile(pattern, flags)
pos = 0
while True:
match = regex.search(string, pos)
if not match:
break
yield match
pos = match.start() + 1
(N[^P](?:S|T)[^P])
Edit live on Debuggex