Python re sub replace with matched content

Question

Trying to get to grips with regular expressions in Python  I m trying to output some HTML highlighted in part of a URL  My input is  images  id size   my output should be  images  lt span gt  id lt  span gt  size   If I do this in Javascript  method    images  id size   method   method replace      a-z        lt span gt  1 lt  span gt    alert method    I get the desired result  but if I do this in Python   gt  gt  gt  method    images  id huge   gt  gt  gt  re sub      a-z        lt span gt  1 lt  span gt    method   images  lt span gt  1 lt  span gt  huge    I don t  how do I get Python to return the correct result rather than  1  Is re sub even the right function to do this

User · Answer

For the replacement portion  Python uses  1 the way sed and vi do  not  1 the way Perl  Java  and Javascript  amongst others  do   Furthermore  because  1 interpolates in regular strings as the character U 0001  you need to use a raw string or  escape it   Python 3 2  r32 88445  Jul 27 2011  13 41 33    GCC 4 0 1  Apple Inc  build 5465   on darwin Type  help    copyright    credits  or  license  for more information   gt  gt  gt  method    images  id huge   gt  gt  gt  import re  gt  gt  gt  re sub     a-z      r  lt span gt  1 lt  span gt    method   images  lt span gt id lt  span gt  huge   gt  gt  gt

User · Answer

Use  1 instead of  1       number Matches the contents of the group of the same number    http   docs python org library re html regular-expression-syntax

User · Answer

Simply use  1 instead of  1   In  1   import re  In  2   method    images  id huge   In  3   re sub r    a-z      r  lt span gt  1 lt  span gt    method  Out 3    images  lt span gt  id lt  span gt  huge    Also note the use of raw strings  r       for regular expressions  It is not mandatory but removes the need to escape backslashes  arguably making the code slightly more readable

User · Answer

A backreference to the whole match value is  g lt 0 gt   see re sub documentation      The backreference  g lt 0 gt  substitutes in the entire substring matched by the RE    See the Python demo   import re method    images  id huge  print re sub r   a-z     r  lt span gt  g lt 0 gt  lt  span gt    method       gt  images  lt span gt  id lt  span gt  huge

[python] Python re.sub replace with matched content

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