Editing specific line in text file in Python

Question

Let s say I have a text file containing   Dan Warrior 500 1 0   Is there a way I can edit a specific line in that text file  Right now I have this      usr bin env python import io  myfile   open  stats txt    r   dan   myfile readline   print dan print  Your name      dan split   n   0   try      myfile   open  stats txt    a       myfile writelines  Mage   1  except IOError          myfile close   finally          myfile close     Yes  I know that myfile writelines  Mage   1  is incorrect  But you get my point  right  I m trying to edit line 2 by replacing Warrior with Mage  But can I even do that

User · Answer

def replace line file name  line num  text       lines   open file name   r   readlines       lines line num    text     out   open file name   w       out writelines lines      out close     And then   replace line  stats txt   0   Mage

User · Answer

You can do it in two ways  choose what suits your requirement   Method I   Replacing using line number  You can use built-in function enumerate   in this case   First  in read mode get all data in a variable  with open  your file txt   r   as f      get all f readlines     Second  write to the file  where enumerate comes to action    with open  your file txt   w   as f      for i line in enumerate get all 1              STARTS THE NUMBERING FROM 1  by default it begins with 0              if i    2                                  OVERWRITES line 2             f writelines  Mage n           else              f writelines line    Method II   Using the keyword you want to replace   Open file in read mode and copy the contents to a list  with open  some file txt   r   as f      newline        for word in f readlines                    newline append word replace  Warrior   Mage        Replace the keyword while you copy       Warrior  has been replaced by  Mage   so write the updated data to the file   with open  some file txt   w   as f      for line in newline          f writelines line    This is what the output will be in both cases   Dan                   Dan            Warrior   ------ gt      Mage        500                   500            1                     1    0                     0

User · Answer

This is the easiest way to do this  fin   open  quot a txt quot   f   open  quot file txt quot    quot wt quot   for line in fin      f write  line replace  foo    bar     fin close   f close    I hope it will work for you

User · Answer

Suppose I have a file named file name as following   this is python it is file handling this is editing of line   We have to replace line 2 with  modification is done    f open  file name   r    a f readlines   for line in f     if line startswith  rai          p a index line   so now we have the position of the line which to be modified a p   modification is done  f seek 0  f truncate    ersing all data from the file f close    so now we have an empty file and we will write the modified content now in the file o open  file name   w   for i in a     o write i  o close    now the modification is done in the file

User · Answer

I have been practising working on files this evening and realised that I can build on Jochen s answer to provide greater functionality for repeated multiple use  Unfortunately my answer does not address issue of dealing with large files but does make life easier in smaller files   with open  filetochange txt    r    as foo      data   foo readlines                     reads file as list     pos   int input  Which position in list to edit     -1   list position to edit     data insert pos   more foo    n              inserts before item to edit     x   data pos 1      data remove x                        removes item to edit     foo seek 0                       seeks beginning of file     for i in data          i strip                      strips   n  from list items         foo write str i

User · Answer

read file lines and edit specific item  file open  quot pythonmydemo txt quot   r   a file readlines   print a 0  6 11    a 0  a 0  0 5    Ericsson n  print a 0    file open  quot pythonmydemo txt quot   w   file writelines a  file close   print a

User · Answer

If your text contains only one individual   import re    creation with open  pers txt   wb   as g      g write  Dan  n Warrior  n 500  r n 1  r 0     with open  pers txt   rb   as h      print  exact content of pers txt before treatment  n  repr h read    with open  pers txt   rU   as h      print   nrU-display of pers txt before treatment  n  h read       treatment def roplo file name what       patR   re compile       r n    r n      r n         with open file name  rb    as f          ch   f read           f seek 0          f write patR sub    1  what ch   roplo  pers txt   Mage       after treatment with open  pers txt   rb   as h      print   nexact content of pers txt after treatment  n  repr h read    with open  pers txt   rU   as h      print   nrU-display of pers txt after treatment  n  h read     If your text contains several individuals   import re    creation with open  pers txt   wb   as g      g write  Dan  n Warrior  n 500  r n 1  r 0  n Jim   n  dragonfly r300 r2 n10 r nSomo ncosmonaut n490 r n3 r65    with open  pers txt   rb   as h      print  exact content of pers txt before treatment  n  repr h read    with open  pers txt   rU   as h      print   nrU-display of pers txt before treatment  n  h read       treatment def ripli file name who what       with open file name  rb    as f          ch   f read           x y   re search    s   who   s   r n      r n     ch re MULTILINE  span 1          f seek x          f write what ch y    ripli  pers txt   Jim   Wizard       after treatment with open  pers txt   rb   as h      print  exact content of pers txt after treatment  n  repr h read    with open  pers txt   rU   as h      print   nrU-display of pers txt after treatment  n  h read     If the    job    of an individual was of a constant length in the texte  you could change only the portion of texte corresponding to the    job    the desired individual  that   s the same idea as senderle   s one   But according to me  better would be to put the characteristics of individuals in a dictionnary recorded in file with cPickle   from cPickle import dump  load  with open  cards   wb   as f      dump   Dan    Warrior  500 1 0   Jim    dragonfly  300 2 10   Somo    cosmonaut  490 3 65   f   with open  cards   rb   as g      id cards   load g  print  id cards before change    id cards  id cards  Jim   0     Wizard   with open  cards   w   as h      dump id cards h   with open  cards   as e      id cards   load e  print   nid cards after change    id cards

User · Answer

You want to do something like this     with is like your try    finally block in this case with open  stats txt    r   as file        read a list of lines into data     data   file readlines    print data print  Your name      data 0     now change the 2nd line  note that you have to add a newline data 1     Mage n     and write everything back with open  stats txt    w   as file      file writelines  data     The reason for this is that you can t do something like  change line 2  directly in a file  You can only overwrite  not delete  parts of a file - that means that the new content just covers the old content  So  if you wrote  Mage  over line 2  the resulting line would be  Mageior

User · Answer

you can use fileinput to do in place editing  import fileinput for  line in fileinput FileInput  myfile   inplace 1       if line                 print line

[python] Editing specific line in text file in Python

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