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Python to search text file string and replace it

P: 20
Hi ,

i am in the middle of creating the script to match the string and replace it

in mount.txt
mickey:/work1 /work1 bla bla bla
mickey:/work2 /work2 bla bla bla
micket:/job /job bla bla bla


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  1. #!/usr/bin/python
  2. import string
  3. s = open("/usr2/py/mount.txt","r+")
  4. for line in s.readlines():
  5.    print line
  6.    string.replace(line, 'mickey','minnie')
  7.    print line
  8. s.close()
  9.  
However, the string.replace seems not working, any advice??? Thank you!

I am using CentOS 4.6 and the python is 2.3.4
Jun 4 '09 #1
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7 Replies


bvdet
Expert Mod 2.5K+
P: 2,851
Hello DannyMc,

string.replace() does not modify the argument string in place, but returns a modified string. You must make an assignment. Unless your file is very large, I would suggest updating the text in the file by reading the file, modifying the text, and writing the modified text back to the file. You can use string method replace() instead of importing the string module.
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  1. s = open("mount.txt").read()
  2. s = s.replace('mickey', 'minnie')
  3. f = open("mount.txt", 'w')
  4. f.write(s)
  5. f.close()
Jun 4 '09 #2

P: 20
thanks for the solution bvdet!!
Jun 5 '09 #3

Expert 100+
P: 511
you can use fileinput for inplace editing
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  1. import fileinput
  2. for line in fileinput.FileInput("file", inplace=1):
  3.     line=line.replace("old","new")
  4.     print line
  5.  
Jun 11 '09 #4

P: 20
Hi guys, i managed to solve my problem with the following scripts:

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  1. #!/usr/bin/python
  2. import re
  3. #fstab location, use w mode as need to overwrite whole file.
  4. s = open("/usr2/py/mount.txt","r")
  5. #temp txt file to store new mount.
  6. tmpfile = open("/usr2/py/tmp.txt","a")
  7. #new nas mount point
  8. newmount = open("/usr2/py/newmount.txt","r")
  9. #search pg-swnas1 line
  10. for line in s.readlines():
  11.     if re.search("filer", line, re.IGNORECASE) != None:
  12.         print line
  13.     else:
  14.         tmpfile.write(line)
  15. #read the latest mount point
  16. readmount = newmount.read()
  17. #append to temp file
  18. tmpfile.write(readmount)
  19. s.close()
  20. tmpfile.close()
  21. tmpfile = open("/usr2/py/tmp.txt","r")
  22. readtmp = tmpfile.read()
  23. s = open("/usr2/py/mount.txt","w")
  24. s.write(readtmp)
  25.  
  26. tmpfile.close()
  27. newmount.close()
  28.  
  29.  
Though the code works, but it seems not a clean code. Is there anyway to simplify it???
Jun 25 '09 #5

bvdet
Expert Mod 2.5K+
P: 2,851
I am a bit unclear about what mount.txt and newmount.txt contain and what you need to replace. You do not need re. You can test for membership with the in operator. If I understand correctly, this should work (untested):
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  1. mountList = open("/usr2/py/mount.txt", "r").readlines()
  2. newmountList = open("/usr2/py/newmount.txt","r").readlines()
  3. outputList = [item for item in mountList if "filer" not in item.lower()]
  4. outputList.extend(newmountList)
  5. f = open("/usr2/py/mount.txt","w")
  6. f.write(''.join(outputList))
  7. f.close()
Jun 25 '09 #6

P: 1
Works nice, thanks !
Aug 9 '17 #7

P: 1
hi bvdet,

The script works fine for single file but how can i replace for multiple files in a directory .

could you write the script please .
My file extensions are .xlf
folder c:/mrit/

with kind regards,
MJ
2 Weeks Ago #8

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