Reformating an external file and then saving it, from inside a python code

Sorry for the basic question, but my python is a bit rusty after having not worked with it for a few months!

Basically I am trying to run a python code over a li开发者_如何学JAVAst of files which are the output of another code (which unfortunately I cannot alter). The problem is that the code I have written requires the files in "input.txt" to all be on separate lines and currently they are separated by a comma.

Try as I might I haven't been able to write anything that reformats this file inside my code.

The files currently look like:

file1,file2,file3

and I need to get them to look like:

file1
file2
file3

and then re save "input.txt" before using it in:

 for ln in open("input.txt"):
    ch.Add(ln.strip())

(where ch is a chain)

Any help would be much appreciated, thanks!

def generateFromFile ( fileName ):
    for line in open( fileName ):
        for segment in line.split( ',' ):
            yield segment

for ln in generateFromFile( "input.txt" ):
    ch.Add( ln.strip() )

for x in files.split(','):
     print >> input, x