I am having some trouble cooking up a regex that produces this result:
Mike1, misha1,2, miguel1,2,3,4,5,6,7,18, and Michea2,3
How does one step back in regex and discard the last match? That is I need a comma before a space to not match. This what I came up with...
\d+(,|\r)
Mike1, misha1,2, miguel1,2,3,4,5,6,7,18, and Micheal2,3
The regex feature you're asking about is called a positive lookbehind. But in your case, I don't think you need it. Try this:
\d+(?:,\d+)*
In your example, this will match the comma delimited lists of numbers and exclude the names and trailing commas and whitespace.
Here is a short bit of test code written in PHP that verifies it on your input:
<?php
$input = "Mike1, misha1,2, miguel1,2,3,4,5,6,7,18, and Micheal2,3";
$matches = array();
preg_match_all('/\d+(?:,\d+)*/', $input, $matches);
print_r($matches[0]);
?>
outputs:
Array
(
[0] => 1
[1] => 1,2
[2] => 1,2,3,4,5,6,7,18
[3] => 2,3
)
I believe \d+,(?!\s) will do what you want. The ?! is a negative lookahead, which only matches if what follows the ?! does not appear at this position in the search string.
>>> re.findall(r'\d+,(?!\s)', 'Mike1, misha1,2, miguel1,2,3,4,5,6,7,18, and Michea2,3')
['1,', '1,', '2,', '3,', '4,', '5,', '6,', '7,', '2,']
Or if you want to match the comma-separated list of numbers excluding the final comma use \d+(?:,\d+)*.
>>> re.findall(r'\d+(?:,\d+)*', 'Mike1, misha1,2, miguel1,2,3,4,5,6,7,18, and Michea2,3')
['1', '1,2', '1,2,3,4,5,6,7,18', '2,3']
Related
I am trying to split texts into "steps"
Lets say my text is
my $steps = "1.Do this. 2.Then do that. 3.And then maybe that. 4.Complete!"
I'd like the output to be:
"1.Do this."
"2.Then do that."
"3.And then maybe that."
"4.Complete!"
I'm not really that good with regex so help would be great!
I've tried many combination like:
split /(\s\d.)/
But it splits the numbering away from text
I would indeed use split. But you need to exclude the digit from the match by using a lookahead.
my #steps = split /\s+(?=\d+\.)/, $steps;
All step-descriptions start with a number followed by a period and then have non-numbers, until the next number. So capture all such patterns
my #s = $steps =~ / [0-9]+\. [^0-9]+ /xg;
say for #s;
This works only if there are surely no numbers in the steps' description, like any approach relying on matching a number (even if followed by a period, for decimal numbers)†
If there may be numbers in there, we'd need to know more about the structure of the text.
Another delimiting pattern to consider is punctuation that ends a sentence (. and ! in these examples), if there are no such characters in steps' description and there are no multiple sentences
my #s = $steps =~ / [0-9]+\. .*? [.!] /xg;
Augment the list of patterns that end an item's description as needed, say with a ?, and/or ." sequence as punctuation often goes inside quotes.‡
If an item can have multiple sentences, or use end-of-sentence punctuation mid-sentence (as a part of a quotation perhaps) then tighten the condition for an item's end by combining footnotes -- end-of-sentence punctuation and followed by number+period
my #s = $steps =~ /[0-9]+\. .*? (?: \."|\!"|[.\!]) (?=\s+[0-9]+\. | \z)/xg;
If this isn't good enough either then we'd really need a more precise description of that text.
† An approach using a "numbers-period" pattern to delimit item's description, like
/ [0-9]+\. .*? (?=\s+[0-9]+\. | \z) /xg;
(or in a lookahead in split) fails with text like
1. Only $2.50 or 1. Version 2.4.1 ...
‡ To include text like 1. Do "this." and 2. Or "that!" we'd want
/ [0-9]+\. .*? (?: \." | !" | [.!?]) /xg;
Following sample code demonstrates power of regex to fill up %steps hash in one line of code.
Once the data obtained you can dice and slice it anyway your heart desires.
Inspect the sample for compliance with your problem.
use strict;
use warnings;
use feature 'say';
use Data::Dumper;
my($str,%steps,$re);
$str = '1.Do this. 2.Then do that. 3.And then maybe that. 4.Complete!';
$re = qr/(\d+)\.(\D+)\./;
%steps = $str =~ /$re/g;
say Dumper(\%steps);
say "$_. $steps{$_}" for sort keys %steps;
Output
$VAR1 = {
'1' => 'Do this',
'2' => 'Then do that',
'3' => 'And then maybe that'
};
1. Do this
2. Then do that
3. And then maybe that
I have the HTML markup of a web page as $subject. I'm using preg_match to search for a particular string artist_x? and trying to return just the x portion. x can be any number ranging from 1 to 12 digits. So, the pattern would have to match any/all of the following:
artist_1?
artist_12345?
artist_123456789012?
...and bring back:
1
12345
123456789012
...respectively.
This is the closest I can come up with:
$pattern = '|[artist_][0-9]{1,12}|';
preg_match($pattern, $subject, $matches);
But it's not working right... It's finding the string I'm looking for and even returning the expected number, but the returned number still has the underscore prepended. I've tried quite a few solutions to get this far, but am out of ideas.
Thanks!
I don't really understand what your pattern is supposed to do.
Anyway, this should work: you just capture the number that interest you. $matches will be an array containing first the whole match and then the group. So the first group will be what you want.
$subject = "artist_3333";
$pattern = '/artist_(\d{1,12})/';
preg_match($pattern, $subject, $matches);
echo($matches[1]); // 3333
\d in here means the same thing as [0-9], it matches digits
I want to match a pattern from text and then append it at the end of line. In below case i want to match numbers and then paste it at the end of line. In case of matching two patterns want to have comma separated.
Basically i am looking how i can use the matching portion as variable.
I am looking to do it in Bash.
abc 123=
agdaf456ad
dfaf879:
abc123xyz12:
To
abc 123=123
agdaf456ad456
dfaf879:879
abc123xyz12:123,12
Something like
(\d+)(.*)$
And replace with
$1$2$1
Regex Demo
Example
$replace = preg_replace("/(\d+)(.*)$/", "$1$2$1", "abc 123=");
echo $replace;
=> abc 123=123
To get all sequences of digits in a given string, you can use a mere \d+ regex, and then just implode the obtained result array and append it to the input string:
$str = "abc123xyz12:";
preg_match_all('/\d+/', $str, $m);
$append = implode(",", $m[0]);
echo $str . $append;
See demo
I am looking to do a 2-step regular expression look-up in Perl, I have text that looks like this:
here is some text 9337 more text AA 2214 and some 1190 more BB stuff 8790 words
I also have a hash with the following values:
%my_hash = ( 9337 => 'AA', 2214 => 'BB', 8790 => 'CC' );
Here's what I need to do:
Find a number
Look up the text code for the number using my_hash
Check if the text code appears within 50 characters of the identified number, and if true print the result
So the output I'm looking for is:
Found 9337, matches 'AA'
Found 2214, matches 'BB'
Found 1190, no matches
Found 8790, no matches
Here's what I have so far:
while ( $text =~ /(\d+)(.{1,50})/g ) {
$num = $1;
$text_after_num = $2;
$search_for = $my_hash{$num};
if ( $text_after_num =~ /($search_for)/ ) {
print "Found $num, matches $search_for\n";
}
else {
print "Found $num, no matches\n";
}
This sort of works, except that the only correct match is 9337; the code doesn't match 2214. I think the reason is that the regular expression match on 9337 is including 50 characters after the number for the second-step match, and then when the regex engine starts again it is starting from a point after the 2214. Is there an easy way to fix this? I think the \G modifier can help me here, but I don't quite see how.
Any suggestions or help would be great.
You have a problem with greediness. The 1,50 will consume as much as it can. Your regex should be /(\d+)(.+?)(?=($|\d))/
To explain, the question mark will make the multiple match non-greedy (it will stop as soon as the next pattern is matched - the next pattern gets precedence). The ?= is a lookahead operator to say "check if the next element is a digit. If so, match but do not consume." This allows the first digit to get picked up by the beginning of the regex and be put into the next matched pattern.
[EDIT]
I added an optional end value to the lookahead so that it wouldn't die on the last match.
Just use :
/\b\d+\b/g
Why match everything if you don't need to? You should use other functions to determine where the number is :
/(?=9337.{1,50}AA)/
This will fail if AA is further than 50 chars away from the end of 9337. Of course you will have to interpolate your variables to match your hashe's keys and values. This was just an example for your first key/value pair.
I have a string which is something like:
prefix::key0==value0::key1==value1::key2==value2::key3==value3::key4==value4::
I want to retrieve the value associated to a key (say, key1). The following pattern:
::key1==([^:]*)
...will work only if there are no ':' character in the value, so I want to make sure the pattern matching will stop only for the substring ::, but I'm can't find how to do that, as most examples I see are about single character matching.
How do I modify the regexp pattern to match all characters between "::key1==" and the next "::" ?
Thanks!
Can you do something like this : ::key1==(.*?)::? Assuming the language supports the lazy ? operator, this should work.
As mentioned in my comment to your question, if the entirety of your string is
prefix::key0==value0::key1==value1::key2==value2::key3==value3::key4==value4::
I would suggest exploding/splitting the string at :: instead of using regex as it will usually always be faster. You didn't specify language but here is a php example:
// string
$string = "prefix::key0==value0::key1==value1::key2==value2::key3==value3::key4==value4::";
// explode using :: as delimiter
$string = explode('::',$string);
// for each element...
foreach ($string as $value) {
// check if it has == in it
if (strpos($value,'==')!==false) $matches[] = $value;
}
// output
echo "<pre>";print_r($matches);
output:
Array
(
[0] => key0==value0
[1] => key1==value1
[2] => key2==value2
[3] => key3==value3
[4] => key4==value4
)
However, if you insist on the regex approach, here negative look-ahead alternative
::((?:(?!::).)+)
php example
// string
$string = "prefix::key0==value0::key1==value1::key2==value2::key3==value3::key4==value4::";
preg_match_all('~::((?:(?!::).)+)~',$string,$matches);
//output
echo "<pre>";print_r($matches);
output
Array
(
[0] => key0==value0
[1] => key1==value1
[2] => key2==value2
[3] => key3==value3
[4] => key4==value4
)
I think you're looking for a positive look-ahead:
::key0==(.*?)(?=::\w+==)
With the following:
prefix::key0==val::ue0::key1==value1::key2==value2::key3==value3::key4==value4::
It correctly finds val::ue0. This also assumes the keys conform to \w ([0-9A-Za-z_])
Also, a positive look-ahead may be a bit of overkill, but will work if the answer contains ::, too.