How to modify a file recursively within a directory

I have a php script with the same file name located in 24 different subdirectories of a parent directory.  Due to changes in the path structure, I need to modify a path on line 7 of each file.  I don't know which language is best suited to this sort of thing but picked python because I'm trying to learn it.  I thought I would start by using csv reader to modify a single file, but even that doesn't work (see below).  

I'm trying to change characters 29 - 36 of line 7 from 'archives' to 'archive_hours' and leave the rest of the line unchanged.  I can print my change (the path variable) to stdout, but only if I quote the line as a string, which defeats the purpose of having a script at all (given that the last part of each path on line 7 is unique).  

Needless to say, I'm unable to change line 7, so the lines that are written to dest currently mirror the original file.  At one point I got the changes to stick but only by defining a new line quoted as a string, and even then the line in the destination file was printed as a list, with each character separated by a comma.  

So the first thing I need to learn is which changes need to happen in what order.  I'm assuming that the command I used to fix the path is incorrect because it creates a string which can't be joined to a list.  But I don't know how else to replace that part of the path -- do I use line.del[29:36] and then line.insert[29:36] with the change to the path?  Whatever I've attempted so far gives me attribute errors.

I've spent enough time on this by now to have manually made the changes several times over, so I figured it was time to ask EE.  My follow-up questions - how to get rid of the windows line returns (^M) and of course how to run this (or another) script so that it will look for the same file name in each subdirectory and make the change - can be deferred as needed (let me know if I'll need to open new questions for that).

TIA
Start Free Trial

1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:

#!/usr/bin/python
 
import csv
 
fin = open('sort_archives.php', 'rb')
source = csv.reader(fin)
fout = open('hr_archives.php', 'wb')
dest = csv.writer(fout)
index = 0
for n, line in enumerate(source):
    if n == 6:
          line = "$myDir='/path-to/archives/archive1';"
          path = str(line[29:36]).replace('archive', 'archive_hours')
          print path
          print line[0:]
    dest.writerow(line)
fin.close()
fout.close()