[Tutor] replacing a string in files in a directory

[Michael Lange]

On Fri, 20 Aug 2004 16:44:15 -0400
Manon.Lamothe at ingcanada.com wrote:

> This is my code
> 
> bbvardir = '/home/bb/bb19c/ext/manon'
> bbvarfiles = os.listdir(bbvardir)
> 
> for item in bbvarfiles:
>      dirfile = os.path.join(bbvardir, item)
>      print '_______________________________________'
>      bbfile = open(dirfile, 'r+')
>      lines = bbfile.readlines()
>      if len(lines) >= 1:
>          firstline = lines[0].strip()
>          print 'firstline ' + firstline
>          colour = firstline.split()[0]
>          print 'colour ' + colour
>          if colour == 'red':
>               withchange = string.replace(firstline,'red','green_green')
>               # withchnage = withchange + '\n'
>               print 'withchange: ' + withchange
>               bbfile.seek(0)
>               bbfile.writelines(withchange)
> 
>          bbfile.close()
> 
> my replacement string is longer than the original one, and when I write the
> replacement in the file, the second line is overwritten.
> 
> This is the original file:
> red bonjour tous le monde 1
> ceci est ma 2ieme ligne ici
> red
> 
> and the final file:
> green_green bonjour tous le monde 1
> t ma 2ieme ligne ici
> red
> 
> How can I fix that code ?
> 

Hi Manon,

if you just want to change the first line in your files, you might want to have a look at the fileinput
module, which has very nice methods for this. With fileinput.input(filename, inplace=1) you can iterate over
the lines in the file and change it's contents on the fly;
and with fileinput.isfirstline() you can check if the current line is the first line in the file.

I hope this helps

Michael