Python string replace regular expression

Question

I have a parameter file of the form   parameter-name parameter-value   Where the parameters may be in any order but there is only one parameter per line   I want to replace one parameter s parameter-value with a new value   I am using a line replace function posted previously to replace the line which uses Python s string replace pattern  sub    The regular expression that I m using works for instance in vim but doesn t appear to work in string replace      Here is the regular expression that I m using   line replace     interfaceOpDataFile    i    interfaceOpDataFile  s     fileIn     Where  interfaceOpDataFile  is the parameter name that I m replacing   i for case-insensitive  and the new parameter value is the contents of the fileIn variable    Is there a way to get Python to recognize this regular expression or else is there another way to accomplish this task

User · Accepted Answer

str replace   v2 v3 does not recognize regular expressions    To perform a substitution using a regular expression  use re sub   v2 v3   For example   import re  line   re sub             r   i    interfaceOpDataFile                   interfaceOpDataFile  s    fileIn              line            In a loop  it would be better to compile the regular expression first   import re  regex   re compile r    interfaceOpDataFile      re IGNORECASE  for line in some file      line   regex sub  interfaceOpDataFile  s    fileIn  line        do something with the updated line

User · Answer

You are looking for the re sub function   import re s    Example String  replaced   re sub   ES     a   s  print replaced    will print axample atring

User · Answer

re sub is definitely what you are looking for   And so you know  you don t need the anchors and the wildcards   re sub r   i interfaceOpDataFile    interfaceOpDataFile  s    filein  line    will do the same thing--matching the first substring that looks like  interfaceOpDataFile  and replacing it

User · Answer

As a summary   import sys import re  f   sys argv 1  find   sys argv 2  replace   sys argv 3  with open  f   r   as myfile       s myfile read   ret   re sub find replace  s       lt  lt  lt  This is where the magic happens print ret

[python] Python string.replace regular expression

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