Python extract pattern matches

Question

Python 2 7 1 I am trying to use python regular expression to extract words inside of a pattern  I have some string that looks like this  someline abc someother line name my user name is valid some more lines   I want to extract the word  my user name   I do something like  import re s    that big string p   re compile  name    is valid   re flags  p match s   this gives me  lt  sre SRE Match object at 0x026B6838 gt    How do I extract my user name now

User · Answer

You could use something like this   import re s    that big string   the parenthesis create a group with what was matched   and   w  matches only alphanumeric charactes p   re compile  name    w    is valid   re flags    use search    so the match doesn t have to happen    at the beginning of  big string  m   p search s    search   returns a Match object with information about what was matched if m      name   m group 1  else      raise Exception  name not found

User · Answer

It seems like you re actually trying to extract a name vice simply find a match  If this is the case  having span indexes for your match is helpful and I d recommend using re finditer  As a shortcut  you know the name part of your regex is length 5 and the is valid is length 9  so you can slice the matching text to extract the name   Note - In your example  it looks like s is string with line breaks  so that s what s assumed below       covert s to list of strings separated by line  s2   s splitlines       find matches by line   for i  j in enumerate s2       matches   re finditer  name      is valid   j         ignore lines without a match     if matches             loop through match group elements         for k in matches                 get text             match txt   k group 0                 get line span             match span   k span 0                 extract username             my user name   match txt 5 -9                 compare with original text             print f Extracted Username   my user name  - found on line  i                print  Match Text    match txt

User · Answer

Maybe that s a bit shorter and easier to understand   import re text        someline abc    someother line    name my user name is valid   some more lines   gt  gt  gt  re search  name      is valid   text  group 1   my user name

User · Answer

You can use groups  indicated with     and      to capture parts of the string  The match object s group   method then gives you the group s contents    gt  gt  gt  import re  gt  gt  gt  s    name my user name is valid   gt  gt  gt  match   re search  name      is valid   s   gt  gt  gt  match group 0     the entire match  name my user name is valid   gt  gt  gt  match group 1     the first parenthesized subgroup  my user name    In Python 3 6  you can also index into a match object instead of using group      gt  gt  gt  match 0     the entire match   name my user name is valid   gt  gt  gt  match 1     the first parenthesized subgroup  my user name

User · Answer

Here s a way to do it without using groups  Python 3 6 or above     gt  gt  gt  re search  2 d d d 01  d 0-3  d    report 20191207 xml   0   20191207

User · Answer

You need to capture from regex  search for the pattern  if found  retrieve the string using group index   Assuming valid checks are performed   gt  gt  gt  p   re compile  quot name      is valid quot    gt  gt  gt  result   p search s   gt  gt  gt  result  lt  sre SRE Match object at 0x10555e738 gt   gt  gt  gt  result group 1        group 1  will return the 1st capture  stuff within the brackets                             group 0  will returned the entire matched text   my user name

User · Answer

You can also use a capture group   P lt user gt pattern  and access the group like a dictionary match  user     string      someline abc n             someother line n             name my user name is valid n             some more lines n     pattern   r name   P lt user gt     is valid  matches   re search pattern  str string   re DOTALL  print matches  user       my user name

User · Answer

You can use matching groups   p   re compile  name      is valid     e g    gt  gt  gt  import re  gt  gt  gt  p   re compile  name      is valid    gt  gt  gt  s           someline abc     someother line     name my user name is valid     some more lines     gt  gt  gt  p findall s    my user name     Here I use re findall rather than re search to get all instances of my user name   Using re search  you d need to get the data from the group on the match object    gt  gt  gt  p search s     gives a match object or None if no match is found  lt  sre SRE Match object at 0xf5c60 gt   gt  gt  gt  p search s  group    entire string that matched  name my user name is valid   gt  gt  gt  p search s  group 1   first group that match in the string that matched  my user name      As mentioned in the comments  you might want to make your regex non-greedy   p   re compile  name       is valid     to only pick up the stuff between  name   and the next   is valid   rather than allowing your regex to pick up other   is valid  in your group

User · Answer

You want a capture group   p   re compile  name      is valid   re flags    parentheses for capture groups print p match s  groups     This gives you a tuple of your matches

[python] Python extract pattern matches

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