How to input a regex in string replace

Question

I need some help on declaring a regex  My inputs are like the following   this is a paragraph with lt  1 gt  in between lt   1 gt  and then there are cases     where the lt  99 gt  number ranges from 1-100 lt   99 gt    and there are many other lines in the txt files with lt  3 gt  such tags  lt   3 gt    The required output is   this is a paragraph with in between and then there are cases     where the number ranges from 1-100   and there are many other lines in the txt files with such tags   I ve tried this      usr bin python import os  sys  re  glob for infile in glob glob os path join os getcwd       txt         for line in reader           line2   line replace   lt  1 gt                 line   line2 replace   lt   1 gt                 line2   line replace   lt  1 gt                line   line2 replace   lt   1 gt                 print line   I ve also tried this  but it seems like I m using the wrong regex syntax        line2   line replace   lt    gt             line   line2 replace   lt     gt             line2   line replace   lt    gt            line   line2 replace   lt     gt          I dont want to hard-code the replace from 1 to 99

User · Answer

I would go like this  regex explained in comments    import re    If you need to use the regex more than once it is suggested to compile it  pattern   re compile r  lt   0     d  gt        lt    0     d  gt       Match the character     lt     literally    lt      Match the character         literally      0          Between zero and unlimited times  as many times as possible  giving back as needed  greedy     0       Match the character         literally          Match a single digit 0  9    d         Between one and unlimited times  as many times as possible  giving back as needed  greedy          Match the character     gt     literally    gt     subject      this is a paragraph with lt  1 gt  in between lt   1 gt  and then there are cases     where the lt  99 gt  number ranges from 1-100 lt   99 gt    and there are many other lines in the txt files with lt  3 gt  such tags  lt   3 gt      result   pattern sub     subject   print result    If you want to learn more about regex I recomend to read Regular Expressions Cookbook by  Jan Goyvaerts and Steven Levithan

User · Answer

import os  sys  re  glob  pattern   re compile r   lt    d  gt    replacementStringMatchesPattern     lt  1 gt    for infile in glob glob os path join os getcwd       txt        for line in reader         retline    pattern sub replacementStringMatchesPattern      line                 sys stdout write retline        print  retline

User · Answer

This tested snippet should do it   import re line   re sub r  lt      d  gt        line    Edit  Here s a commented version explaining how it works   line   re sub r        x    Use free-spacing mode     lt       Match a literal   lt            Optionally match a              Match a literal        d     Match one or more digits    gt       Match a literal   gt              line    Regexes are fun  But I would strongly recommend spending an hour or two studying the basics  For starters  you need to learn which characters are special   metacharacters  which need to be escaped  i e  with a backslash placed in front - and the rules are different inside and outside character classes   There is an excellent online tutorial at  www regular-expressions info  The time you spend there will pay for itself many times over  Happy regexing

User · Answer

The easiest way  import re  txt  this is a paragraph with lt  1 gt  in between lt   1 gt  and then there are cases     where the lt  99 gt  number ranges from 1-100 lt   99 gt    and there are many other lines in the txt files with lt  3 gt  such tags  lt   3 gt    out   re sub    lt    gt    gt         txt  print out

User · Answer

str replace   does fixed replacements  Use re sub   instead

User · Answer

replace method of string objects does not accept regular expressions but only fixed strings  see documentation  http   docs python org 2 library stdtypes html str replace    You have to use re module   import re newline  re sub   lt       0-9   gt        line

User · Answer

don t have to use regular expression  for your sample string    gt  gt  gt  s  this is a paragraph with lt  1 gt  in between lt   1 gt  and then there are cases     where the lt  99 gt  number ranges from 1-100 lt   99 gt    nand there are many other lines in the txt files nwith lt  3 gt  such tags  lt   3 gt  n    gt  gt  gt  for w in s split   gt           if   lt   in w           print w split   lt    0      this is a paragraph with  in between  and then there are cases     where the  number ranges from 1-100   and there are many other lines in the txt files with  such tags

[python] How to input a regex in string.replace?

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