Question

Is there a way to debug a regular expression in Python? And I’m not referring to the process of trying and trying till they work 🙂

Here is how regexes can be debugged in Perl:

 use re 'debug';  my $str = 'GET http://some-site.com HTTP/1.1'; if($str =~/get\s+(\S+)/i) {     print 'MATCH:$1\n'; } 

The code above produces the following output on my computer when ran:

 Compiling REx 'get\s+(\S+)' Final program:    1: EXACTF  (3)    3: PLUS (5)    4:   SPACE (0)    5: OPEN1 (7)    7:   PLUS (9)    8:     NSPACE (0)    9: CLOSE1 (11)   11: END (0) stclass EXACTF  minlen 5 Matching REx 'get\s+(\S+)' against 'GET http://some-site.com HTTP/1.1' Matching stclass EXACTF  against 'GET http://some-site.com HTTP/1.1' (33 chars)    0           |  1:EXACTF (3)    3        |  3:PLUS(5)                                   SPACE can match 1 times out of 2147483647...    4       |  5:  OPEN1(7)    4       |  7:  PLUS(9)                                     NSPACE can match 20 times out of 2147483647...   24       |  9:    CLOSE1(11)   24       | 11:    END(0) Match successful! MATCH:http://some-site.com Freeing REx: 'get\s+(\S+)'  

Answer 1

  >>> p = re.compile('.*', re.DEBUG) max_repeat 0 65535   any None >>>                           

regex '|' operator vs separate runs for each sub-expression