regex - Python re.finditer match.groups() does not contain all groups from match -

i trying use regex in python find , print matching lines multiline search. text searching through may have below example structure:

 aaa abc1 abc2 abc3 aaa abc1 abc2 abc3 abc4 abc aaa abc1 aaa 

from want retrieve abc*s occur @ least once , preceeded aaa.

the problem is, despite group catching want:

match = <_sre.sre_match object; span=(19, 38), match='aaa\nabc2\nabc3\nabc4\n'> 

... can access last match of group:

match groups = ('aaa\n', 'abc4\n') 

below example code use problem.

#! python import sys import re import os  string = "aaa\nabc1\nabc2\nabc3\naaa\nabc1\nabc2\nabc3\nabc4\nabc\naaa\nabc1\naaa\n" print(string)  p_matches = [] p_matches.append( (re.compile('(aaa\n)(abc[0-9]\n){1,}')) ) #    matches = re.finditer(p_matches[0],string)  match in matches:     strout = ''     gr_iter=0     print("match = "+str(match))     print("match groups = "+str(match.groups()))     group in match.groups():     gr_iter+=1     sys.stdout.write("test group:"+str(gr_iter)+"\t"+group) # test output     if group not none:         if group != '':             strout+= '"'+group.replace("\n","",1)+'"'+'\n' sys.stdout.write("\ncomplete result:\n"+strout+"====\n") 

here regular expression:

(aaa\r\n)(abc[0-9]\r\n){1,} 

debuggex demo

your goal capture all abc#s follow aaa. can see in debuggex demo, abc#s indeed being matched (they're highlighted in yellow). however, since "what being repeated" part

abc[0-9]\r\n 

is being captured (is inside parentheses), , quantifier,

{1,} 

is not being captured, therefore causes matches except final one discarded. them, must capture quantifier:

aaa\r\n((?:abc[0-9]\r\n){1,}) 

debuggex demo

i've placed "what being repeated" part (abc[0-9]\r\n) non-capturing group. (i've stopped capturing aaa, don't seem need it.)

the captured text can split on newline, , give pieces wish.

(note \n doesn't work in debuggex. requires \r\n.)

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this workaround. not many regular expression flavors offer capability of iterating through repeating captures (which ones...?). more normal approach loop through , process each match found. here's example java:

   import java.util.regex.*;  public class repeatingcapturegroupsdemo {    public static void main(string[] args) {       string input = "i have cat, dog better.";        pattern p = pattern.compile("(mouse|cat|dog|wolf|bear|human)");       matcher m = p.matcher(input);        while (m.find()) {          system.out.println(m.group());       }    } } 

output:

cat dog 

(from http://ocpsoft.org/opensource/guide-to-regular-expressions-in-java-part-1/, 1/4 down)

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please consider bookmarking stack overflow regular expressions faq future reference. links in answer come it.