Number of regex matches

Question

I m using the finditer function in the re module to match some things and everything is working    Now I need to find out how many matches I ve got  Is it possible without looping through the iterator twice   one to find out the count and then the real iteration   Some code   imageMatches   re finditer   lt img src      P lt path gt  -  w          response 2      lt Here I need to get the number of matches gt  for imageMatch in imageMatches      doStuff   Everything works  I just need to get the number of matches before the loop

User · Answer

I know this is a little old  but this but here is a concise function for counting regex patterns   def regex cnt string  pattern       return len re findall pattern  string    string    abc123   regex cnt string    0-9

User · Answer

If you find you need to stick with finditer    you can simply use a counter while you iterate through the iterator   Example    gt  gt  gt  from re import    gt  gt  gt  pattern   compile r  ython    gt  gt  gt  string    i like python jython and dython  whatever that is    gt  gt  gt  iterator   finditer pattern  string   gt  gt  gt  count   0  gt  gt  gt  for match in iterator          count   1  gt  gt  gt  count 3   If you need the features of finditer    not matching to overlapping instances   use this method

User · Answer

An example for counting matched groups import re  pattern   re compile r   w     d     w     w     re IGNORECASE  search str    My 11 Char String   res   re match pattern  search str  print len res groups       len   4   print  res group 1     My print  res group 2     11 print  res group 3     Char print  res group 4     String

User · Answer

For those moments when you really want to avoid building lists   import re import operator from functools import reduce count   reduce operator add   1 for   in re finditer my pattern  my string       Sometimes you might need to operate on huge strings  This might help

User · Answer

If you always need to know the length  and you just need the content of the match rather than the other info  you might as well use re findall   Otherwise  if you only need the length sometimes  you can use e g   matches   re finditer          matches   tuple matches    to store the iteration of the matches in a reusable tuple   Then just do len matches    Another option  if you just need to know the total count after doing whatever with the match objects  is to use  matches   enumerate re finditer         which will return an  index  match  pair for each of the original matches   So then you can just store the first element of each tuple in some variable   But if you need the length first of all  and you need match objects as opposed to just the strings  you should just do  matches   tuple re finditer

User · Answer

If you know you will want all the matches  you could use the re findall function  It will return a list of all the matches  Then you can just do len result  for the number of matches

[python] Number of regex matches

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