I'm trying for a few hours to write a pattern for some matching algorithm and I can't manage to find something for the following issue: given the example "my_name_is", I need to extract all words individually, as well as the whole expression. Consider that it may be a list of n examples, some that can be matched, some that cannot be matched.
"my_name_is" => ["my", "name", "is", "my_name_is"]
How can I do this, how should the regexp look like? Looking forward for your answers, thank you!
Regular Expressions are patterns used to match a string of characters. We usually use them to validate a string of characters, or to find and replace a specific pattern within text.
Here, it seems the outcome you're looking for is an array of strings that have been split using an underscore. Regex isn't what you're looking for.
Implementation would change based on language, but consider the following code:
function stringToArray(myStr)
{
words = str_split(myStr, '_');
return array_merge(words, [myStr]);
}
use re.findall with the following as your regex:
([^_]+)+?
This should match all sets of consecutive characters that don't contain the underscore.
As for the whole thing? You already have it, so there's no reason to regex the whole string
Related
I am learning regex and trying to write a pattern that exactly matches each of the strings without'-' so that I can iterate for each of the groups and print the respective strings.
I have a string that looks like "Abcd001-wd2s-vwe1-20180e3103.txt"
I was able to write a regex for extracting Abcd001, wd2s and .txt from above text as shown below
(\A[^-]+)=> Abcd001
(-[^-]+-)=> wd2s
(\..*)=>.txt
However, I was unable to come up with the correct pattern for extracting the exact strings vwe1 and 20180e3103
It will be really helpful if you can guide me on this or if there is a better approach to achieve this?
Please note: [^-.]+ may give me all the words separately but I am looking for an option where I have a group defined for each of these strings so that its one to one mapping.
Thanks!
To get vwe1 or 20180e3103 from the example data, you might use a quantifier {2} or {3} to repeat matching one or more word charcters followed by a hyphen (?:\w+-){2}.
Then you could capture in a group ([^-.]+) matching not a hyphen or a dot.
(?:\w+-){2}([^-.]+)
Try the below regex
/\-([^\)]+)\-/gmi;
Also check the similar implementation:
https://stackoverflow.com/a/50336050/8179245
The following is in PHP but the regex will also be used in javascript.
Trying to extract repeating patterns from a string
string can be any of the following:
"something arbitrary"
"D123"
"D111|something"
"D197|what.org|when.net"
"D297|who.197d234.whatever|when.net|some other arbitrary string"
I'm currently using the following regex: /^D([0-9]{3})(?:\|([^\|]+))*/
This correctly does not match the first string, matches the second and third correctly. The problem is the third and fourth only match the Dxxx and the last string. I need each of the strings between the '|' to be matched.
I'm hoping to use a regex as it makes it a single step. I realize I could just detect the leading Dxxx then use explode or split as appropriate to break the strings out. I've just gotten stuck on wanting a single regular expression match step.
This same regex may be used in Python as well so just want a generic regex solution.
There is no way to have a dynamic number of capture groups in a regular expression, but if you know some upper limit to how many parts you would have in one string, you can just repeat the pattern that many times:
/^D([0-9]{3})(?:$|\|)(.*?)(?:$|\|)(.*?)(?:$|\|)(.*?)(?:$|\|)(.*?)(?:$|\|)/
So after the initial ^D([0-9]{3})(?:$|\|) you just repeat (.*?)(?:$|\|) as many times as you need it.
When the string has fewer elements, those remaining capture groups will match the empty string.
See regex tester.
Is something like preg_match_all() (the PHP variant of a global match) also acceptable for you?
Then you could use:
^(?|D([0-9]{3})|^.+$|(?!^)\|([^|\n]*)(?=\||$))
This will match everything in a string in different matches, e.g. take your string:
D197|what.org|when.net
It will you then give three matches:
D197
what.org
when.net
Running live: https://regex101.com/r/jL2oX6/4 (Everything in green are your group matches. Ignore what's in blue.)
I've read various resources and can't find anything which can easily explain how to match this format of string.
Something similar to this below?
/S[0-15][0-15]E[0-24]/
Regex [] matches all single characters in the brackets. You need to split it into multiple part expressions.
Try this:
/S(0?[0-9]|1[0-5])E([01]?[0-9]|2[0-4])/
About the use of the hyphen, pleas read this.
I am trying to create a regex that will match the first 3 characters of a string,
If I have a string ABCFFFF I want to verify that the first 3 characters are ABC.
It's pretty straightforward, the pattern would be ^ABC
As others may point out, using regular expressions for such a task is an overkill. Any programming language with regex support can do it better with simple string manipulations.
Just simple regex will work:
/^ABC/
But is it a good use case for using regex, I am not sure. Consider using substring in whatever language/platform you're using.
"^ABC" should work. '^' matches the start in most regex implementations.
I have an text that consists of information enclosed by a certain pattern.
The only thing I know is the pattern: "${template.start}" and ${template.end}
To keep it simple I will substitute ${template.start} and ${template.end} with "a" in the example.
So one entry in the text would be:
aINFORMATIONHEREa
I do not know how many of these entries are concatenated in the text. So the following is correct too:
aFOOOOOOaaASDADaaASDSDADa
I want to write a regular expression to extract the information enclosed by the "a"s.
My first attempt was to do:
a(.*)a
which works as long as there is only one entry in the text. As soon as there are more than one entries it failes, because of the .* matching everything. So using a(.*)a on aFOOOOOOaaASDADaaASDSDADa results in only one capturing group containing everything between the first and the last character of the text which are "a":
FOOOOOOaaASDADaaASDSDAD
What I want to get is something like
captureGroup(0): aFOOOOOOaaASDADaaASDSDADa
captureGroup(1): FOOOOOO
captureGroup(2): ASDAD
captureGroup(3): ASDSDAD
It would be great to being able to extract each entry out of the text and from each entry the information that is enclosed between the "a"s. By the way I am using the QRegExp class of Qt4.
Any hints? Thanks!
Markus
Multiple variation of this question have been seen before. Various related discussions:
Regex to replace all \n in a String, but no those inside [code] [/code] tag
Using regular expressions how do I find a pattern surrounded by two other patterns without including the surrounding strings?
Use RegExp to match a parenthetical number then increment it
Regex for splitting a string using space when not surrounded by single or double quotes
What regex will match text excluding what lies within HTML tags?
and probably others...
Simply use non-greedy expressions, namely:
a(.*?)a
You need to match something like:
a[^a]*a
You have a couple of working answers already, but I'll add a little gratuitous advice:
Using regular expressions for parsing is a road fraught with danger
Edit: To be less cryptic: for all there power, flexibility and elegance, regular expression are not sufficiently expressive to describe any but the simplest grammars. Ther are adequate for the problem asked here, but are not a suitable replacement for state machine or recursive decent parsers if the input language become more complicated.
SO, choosing to use RE for parsing input streams is a decision that should be made with care and with an eye towards the future.