using functions and file renaming problem

[hokiegal99]

A few questions about the following code. How would I "wrap" this in a 
function, and do I need to?

Also, how can I make the code smart enough to realize that when a file 
has 2 or more bad charcters in it, that the code needs to run until all 
bad characters are gone? For example, if a file has the name 
"<bad*mac\file" the program has to run 3 times to get all three bad 
chars out of the file name.

The passes look like this:

1. <bad*mac\file becomes -bad*mac\file
2. -bad*mac\file becomes -bad-mac\file
3. -bad-mac\file becomes -bad-mac-file

I think the problem is that once the program finds a bad char in a 
filename it replaces it with a dash, which creates a new filename that 
wasn't present when the program first ran, thus it has to run again to 
see the new filename.

import os, re, string
bad = re.compile(r'%2f|%25|[*?<>/\|\\]') #search for these.
print " "
setpath = raw_input("Path to the dir that you would like to clean: ")
print " "
print "--- Remove Bad Charaters From Filenames ---"
print " "
for root, dirs, files in os.walk(setpath):
     for file in files:
         badchars = bad.findall(file)
         newfile = ''
         for badchar in badchars:
             newfile = file.replace(badchar,'-') #replace bad chars.
         if newfile:
             newpath = os.path.join(root,newfile)
             oldpath = os.path.join(root,file)
             os.rename(oldpath,newpath)
	    print oldpath
	    print newpath
print " "
print "--- Done ---"
print " "