Replace string within file contents

Question

How can I open a file  Stud txt  and then replace any occurences of  A  with  Orange

User · Answer

If you d like to replace the strings in the same file  you probably have to read its contents into a local variable  close it  and re-open it for writing   I am using the with statement in this example  which closes the file after the with block is terminated - either normally when the last command finishes executing  or by an exception   def inplace change filename  old string  new string         Safely read the input filename using  with      with open filename  as f          s   f read           if old string not in s              print    old string   not found in  filename    format   locals                 return        Safely write the changed content  if found in the file     with open filename   w   as f          print  Changing   old string   to   new string   in  filename   format   locals             s   s replace old string  new string          f write s    It is worth mentioning that if the filenames were different  we could have done this more elegantly with a single with statement

User · Answer

Something like  file   open  Stud txt   contents   file read   replaced contents   contents replace  A    Orange     lt do stuff with the result gt

User · Answer

with open  Stud txt   r   as f      newlines          for line in f readlines            newlines append line replace  A    Orange    with open  Stud txt    w   as f      for line in newlines          f write line

User · Answer

easiest way is to do it with regular expressions  assuming that you want to iterate over each line in the file  where  A  would be stored  you do     import re  input   file  C  full path Stud txt    r    when you try and write to a file with write permissions  it clears the file and writes only  what you tell it to the file   So we have to save the file first   saved input for eachLine in input      saved input append eachLine    now we change entries with  A  to  Orange  for i in range 0  len old       search   re sub  A    Orange   saved input i       if search is not None          saved input i    search  now we open the file in write mode  clearing it  and writing saved input back to it input   file  C  full path Stud txt    w   for each in saved input      input write each

User · Answer

with open  Stud txt    rt   as fin      with open  out txt    wt   as fout          for line in fin              fout write line replace  A    Orange

User · Answer

usr bin python  with open FileName  as f      newText f read   replace  A    Orange    with open FileName   w   as f      f write newText

User · Answer

Using pathlib  https   docs python org 3 library pathlib html   from pathlib import Path file   Path  Stud txt   file write text file read text   replace  A    Orange      If input and output files were different you would use two different variables for read text and write text    If you wanted a change more complex than a single replacement  you would assign the result of read text to a variable  process it and save the new content to another variable  and then save the new content with write text   If your file was large you would prefer an approach that does not read the whole file in memory  but rather process it line by line as show by Gareth Davidson in another answer  https   stackoverflow com a 4128192 3981273   which of course requires to use two distinct files for input and output

User · Answer

If you are on linux and just want to replace the word dog with catyou can do   text txt   Hi  i am a dog and dog s are awesome  i love dogs  dog dog dogs    Linux Command   sed -i  s dog cat g  test txt   Output   Hi  i am a cat and cat s are awesome  i love cats  cat cat cats    Original Post  https   askubuntu com questions 20414 find-and-replace-text-within-a-file-using-commands

[python] Replace string within file contents

Examples related to python

Examples related to string

Examples related to file-io