I have a list of strings each telling me after how many iterations an algorithm converged.
string_list = [
"Converged after 1 iteration",
"Converged after 20 iterations",
"Converged after 7 iterations"
]
How can I extract the number of iterations? The result woudl be [1, 20, 7]. I tried with regex. Apparently (?<=after )(.*)(?= iteration*) will give me anything in between after and iteration but then this doesn't work:
occursin(string_list[1], r"(?<=after )(.*)(?= iteration*)")
There's a great little Julia package that makes creating regexes easier called ReadableRegex, and as luck would have it the first example in the readme is an example of finding every integer in a string:
julia> using ReadableRegex
julia> reg = #compile look_for(
maybe(char_in("+-")) * one_or_more(DIGIT),
not_after = ".",
not_before = NON_SEPARATOR)
r"(?:(?<!\.)(?:(?:[+\-])?(?:\d)+))(?!\P{Z})"
That regex can now be broadcast over your list of strings:
julia> collect.(eachmatch.(reg, string_list))
3-element Vector{Vector{RegexMatch}}:
[RegexMatch("1")]
[RegexMatch("20")]
[RegexMatch("7")]
To extract information out of a regex, you want to use match and captures:
julia> convergeregex = r"Converged after (\d+) iteration"
r"Converged after (\d+) iteration"
julia> match(convergeregex, string_list[2]).captures[1]
"20"
julia> parse.(Int, [match(convergeregex, s).captures[1] for s in string_list])
3-element Vector{Int64}:
1
20
7
\d+ matches a series of digits (so, the number of iterations here), and the parantheses around it indicates that you want the part of the string matched by that to be placed in the results captures array.
You don't need the lookbehind and lookahead operators (?<=, ?=) here.
Related
I have a set of strings that have some letters, occasional one number, and then somewhere 2 or 3 numbers. I need to match those 2 or 3 numbers.
I have this:
\w*(\d{2,3})\w*
but then for strings like
AAA1AAA12A
AAA2AA123A
it matches '12' and '23' respectively, i.e. it fails to pick the three digits in the second case.
How do I get those 3 digits?
Here is how you would do it in Java.
the regex simply matches on a group of 2 or 3 digits.
the while loop uses find() to continue finding matches and the printing the captured match. The 1 and the 1223 are ignored.
String s= "AAA1AAA12Aksk2ksksk21sksksk123ksk1223sk";
String regex = "\\D(\\d{2,3})\\D";
Matcher m = Pattern.compile(regex).matcher(s);
while (m.find()) {
System.out.println(m.group(1));
}
prints
12
21
123
Looks like the correct answer would be:
\w*?(\d{2,3})\w*
Basically, making preceding expression lazy does the job
I am facing some issues forming a regex that matches at least n times a given pattern within m characters of the input string.
For example imagine that my input string is:
00000001100000001110111100000000000000000000000000000000000000000000000000110000000111000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001100
I want to detect all cases where an 1 appears at least 7 times (not necessarily consecutively) in the input string, but within a window of up to 20 characters.
So far I have built this expression:
(1[^1]*?){7,}
which detects all cases where an 1 appears at least 7 times in the input string, but this now matches both the:
11000000011101111
and the
1100000001110000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000011
parts whereas I want only the first one to be kept, as it is within a substring composed of less than 20 characters.
It tried to combine the aforementioned regex with:
(?=(^[01]{0,20}))
to also match only parts of the string containing either an '1' or a '0' of length up to 20 characters but when I do that it stops working.
Does anyone have an idea gow to accomplish this?
I have put this example in regex101 as a quick reference.
Thank you very much!
This is not something that can be done with regex without listing out every possible string. You would need to iterate over the string instead.
You could also iterate over the matches. Example in Python:
import re
matches = re.finditer(r'(?=((1[^1]*?){7}))', string)
matches = [match.group(1) for match in matches if len(match.group(1)) <= 20]
The next Python snippet is an attempt to get the desired sequences using only the regular expression.
import re
r = r'''
(?mx)
( # the 1st capturing group will contain the desired sequence
1 # this sequence should begin with 1
(?=(?:[01]{6,19}) # let's see that there are enough 0s and 1s in a line
(.*$)) # the 2nd capturing group will contain all characters to the end of a line
(?:0*1){6}) # there must be six more 1s in the sequence
(?=.{0,13} # complement the 1st capturing group to 20 characters
\2) # the rest of a line should be 2nd capturing group
'''
s = '''
0000000
101010101010111111100000000000001
00000001100000001110111100000000000000000000000000000000000000000000000000110000000111000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001100
1111111
111111
'''
print([m.group(1) for m in re.finditer(r, s)])
Output:
['1010101010101', '11111100000000000001', '110000000111011', '1111111']
You can find an exhaustive explanation of this regular expression on RegEx101.
I am having hard time trying to convert the following regular expression into an erlang syntax.
What I have is a test string like this:
1,2 ==> 3 #SUP: 1 #CONF: 1.0
And the regex that I created with regex101 is this (see below):
([\d,]+).*==>\s*(\d+)\s*#SUP:\s*(\d)\s*#CONF:\s*(\d+.\d+)
:
But I am getting weird match results if I convert it to erlang - here is my attempt:
{ok, M} = re:compile("([\\d,]+).*==>\\s*(\\d+)\\s*#SUP:\\s*(\\d)\\s*#CONF:\\s*(\\d+.\\d+)").
re:run("1,2 ==> 3 #SUP: 1 #CONF: 1.0", M).
Also, I get more than four matches. What am I doing wrong?
Here is the regex101 version:
https://regex101.com/r/xJ9fP2/1
I don't know much about erlang, but I will try to explain. With your regex
>{ok, M} = re:compile("([\\d,]+).*==>\\s*(\\d+)\\s*#SUP:\\s*(\\d)\\s*#CONF:\\s*(\\d+.\\d+)").
>re:run("1,2 ==> 3 #SUP: 1 #CONF: 1.0", M).
{match,[{0, 28},{0,3},{8,1},{16,1},{25,3}]}
^^ ^^
|| ||
|| Total number of matched characters from starting index
Starting index of match
Reason for more than four groups
First match always indicates the entire string that is matched by the complete regex and rest here are the four captured groups you want. So there are total 5 groups.
([\\d,]+).*==>\\s*(\\d+)\\s*#SUP:\\s*(\\d)\\s*#CONF:\\s*(\\d+.\\d+)
<-------> <----> <---> <--------->
First group Second group Third group Fourth group
<----------------------------------------------------------------->
This regex matches entire string and is first match you are getting
(Zero'th group)
How to find desired answer
Here we want anything except the first group (which is entire match by regex). So we can use all_but_first to avoid the first group
> re:run("1,2 ==> 3 #SUP: 1 #CONF: 1.0", M, [{capture, all_but_first, list}]).
{match,["1,2","3","1","1.0"]}
More info can be found here
If you are in doubt what is content of the string, you can print it and check out:
1> RE = "([\\d,]+).*==>\\s*(\\d+)\\s*#SUP:\\s*(\\d)\\s*#CONF:\\s*(\\d+.\\d+)".
"([\\d,]+).*==>\\s*(\\d+)\\s*#SUP:\\s*(\\d)\\s*#CONF:\\s*(\\d+.\\d+)"
2> io:format("RE: /~s/~n", [RE]).
RE: /([\d,]+).*==>\s*(\d+)\s*#SUP:\s*(\d)\s*#CONF:\s*(\d+.\d+)/
For the rest of issue, there is great answer by rock321987.
I found somewhat similar questions
R - Select string text between two values, regex for n characters or at least m characters,
but I'm still having trouble
say I have a string in r
testing_String <- "AK ADAK NAS PADK ADK 70454 51 53N 176 39W 4 X T 7"
And I need to be able to pull anything between the first element in the string that contains 2 characters (AK) and PADK,ADK. PADK and ADK will change in character but will always be 4 and 3 characters in length respectively.
So I would need to pull
ADAK NAS
I came up with this but its picking up everything from AK to ADK
^[A-Za-z0_9_]{2}(.*?) +[A-Za-z0_9_]{4}|[A-Za-z0_9_]{3,}
If I understood your question correctly, this should do the trick:
\b[A-Z]{2}\s+(.+?)\s+[A-Z]{4}\s+[A-Z]{3}\b
Demo
You'll have to switch the perl = TRUE option (to use a decent regex engine).
\b means word boundary. So this pattern looks for a match starting with a 2-letter word and ending with a 4 letter word followed by a 3 letter word. Your value will be in the first group.
Alternatively, you can write the following to avoid using the capturing group:
\b[A-Z]{2}\s+\K.+?(?=\s+[A-Z]{4}\s+[A-Z]{3}\b)
But I'd prefer the first method because it's easier to read.
Lookbehind is supported for perl=TRUE, so this regex will do what you want:
(?<=\w{2}\s).*?(?=\s+[^\s]{4}\s[^\s]{2})
I'm using (or I'd like to use) R to extract some information. I have the following sentence and I'd like to split. In the end, I'd like to extract only the number 24.
Here's what I have:
doc <- "Hits 1 - 10 from 24"
And I want to extract the number "24". I know how to extract the number once I can reduce the sentence in "Hits 1 - 10 from" and "24". I tried using this:
n_docs <- unlist(str_split(key_n_docs, ".\\from"))[1]
But this leaves me with: "Hits 1 - 10"
Obviously the split works somehow, but I'm interested in the part after "from" not the one before. All the help is appreciated!
If you want to extract from a single character string:
strsplit(key_n_docs, "from")[[1]][2]
or the equivalent expression used by #BastiM (sorry I saw your answer after I submitted mine)
unlist(strsplit(key_n_docs, "from"))[2]
If you want to extract from a vector of character strings:
sapply(strsplit(key_n_docs, "from"),`[`, 2)
Usually the result of str_split would contain the number you're searching for at index 1, but since you wrap it with unlist it seems you have to increment the index by one. Using
unlist(strsplit("Hits 1 - 10 from 24", "from"))[2]
works like a charm for me.
demo # ideone
You can use str_extract from stringr:
library(stringr)
numbers <- str_extract(doc, "[0-9]+$")
This will give only the numbers in the end of the sentence.
numbers
"24"
You can use sub to extract the number:
sub(".*from *(\\d+).*", "\\1", doc)
# [1] "24"