Python How to use RegEx in an if statement

Question

I have the following code which looks through the files in one directory and copies files that contain a certain string into another directory  but I am trying to use Regular Expressions as  the string could be upper and lowercase or a mix of both    Here is the code that works  before I tried to use RegEx s  import os import re import shutil  def test        os chdir  C  Users David Desktop Test MyFiles       files   os listdir          os mkdir  C  Users David Desktop Test MyFiles2       for x in  files           inputFile   open  x    r           content   inputFile read           inputFile close           if   Hello World  in content              shutil copy x   C  Users David Desktop Test MyFiles2     Here is my code when I have tried to use RegEx s  import os import re import shutil  def test2        os chdir  C  Users David Desktop Test MyFiles       files   os listdir          os mkdir  C  Users David Desktop Test MyFiles2       regex txt    facebook com      for x in  files           inputFile   open  x    r           content   inputFile read           inputFile close           regex   re compile regex txt  re IGNORECASE    Im guessing that I need a line of code that is something like  if regex   re compile regex txt  re IGNORECASE     True   But I cant seem to get anything to work  if someone could point me in the right direction it would be appreciated

User · Answer

First you compile the regex  then you have to use it with match  find  or some other method to actually run it against some input   import os import re import shutil  def test        os chdir  C  Users David Desktop Test MyFiles       files   os listdir          os mkdir  C  Users David Desktop Test MyFiles2       pattern   re compile regex txt  re IGNORECASE      for x in  files           with open  x    r   as input file              for line in input file                  if pattern search line                       shutil copy x   C  Users David Desktop Test MyFiles2                       break

User · Answer

if re search r pattern   string    Simple if-test   if re search r ing b    seeking a great perhaps          any words end with ing      print  yes     Pattern check  extract a substring  case insensitive   match object   re search r  OUGHT      BE     ought to be   flags re IGNORECASE  if match object      assert  to     match object group 1        what s between ought and be    Notes    Use re search   not re match   Match restricts to the start of strings  a confusing convention if you ask me  If you do want a string-starting match  use caret or  A instead  re search r             Use raw string syntax r pattern  for the first parameter  Otherwise you would need to double up backslashes  as in re search  ing  b          In this example   b is a special sequence meaning word-boundary in regex  Not to be confused with backspace  re search   returns None if it doesn t find anything  which is always falsy   re search   returns a Match object if it finds anything   which is always truthy  a group is what matched inside parentheses  group numbering starts at 1 Specs Tutorial

User · Answer

The REPL makes it easy to learn APIs   Just run python  create an object and then ask for help     python  gt  gt  gt  import re  gt  gt  gt  help re compile r       at the command line shows  among other things      search           search string   pos   endpos    --  match object or None    Scan through string looking for a match  and return a corresponding   MatchObject instance  Return None if no position in the string matches    so you can do  regex   re compile regex txt  re IGNORECASE   match   regex search content     From your file reading code  if match is not None      use match   Incidentally   regex txt    facebook com    has a   which matches any character  so re compile  facebook com   search  facebookkcom   is not None is true because   matches any character   Maybe  regex txt   r   i facebook  com    The    matches a literal     character instead of treating   as a special regular expression operator   The r      bit means that the regular expression compiler gets the escape in    instead of the python parser interpreting it   The   i  makes the regex case-insensitive like re IGNORECASE but self-contained

User · Answer

if re match regex  content     blah    You could also use re search depending on how you want it to match

User · Answer

Regex s shouldn t really be used in this fashion - unless you want something more complicated than what you re trying to do - for instance  you could just normalise your content string and comparision string to be   if  facebook com  in content lower        shutil copy x   C  Users David Desktop Test MyFiles2

[python] Python: How to use RegEx in an if statement?

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