Question

I wrote a fast and easy hack to walk thru directories (in stepmania song dir), find conf-files and name the directory the conf-files are in to a certain name found in the conf-file. This works great on my linux box. But not at my wives Windows XP-box running as an admin. I get permission-error. What’s wrong? Here’s the code:

#!/usr/bin/env python
# -*- coding:utf-8 -*-

from __future__ import with_statement

import os
import re
import sys

def renamer(in_path):
    for (path, dirs, files) in os.walk(in_path):
        exts = ['.sm', '.dwi'] # Only search files with this suffix
        conf_files = [] 

        # Create list with conf-files
        for ext in exts:
            conf_files.extend([file for file in files if file.lower().endswith(ext)])

        # Search for conf-files in directory 
        for conf_file in conf_files:
            try:
                with open(os.path.join(path, conf_file)) as f:
                    match = re.search('TITLE:\s?(.*);', f.read()) # Search for whatever follows "TITLE:"
                    new_dir_name = match.group(1) # The new dir-name is whatever the TITLE states in conf-file
                    os.rename(path, os.path.join(path, '..', new_dir_name)) 
            except IndexError:
                print 'No conf-file in', path

if __name__ == '__main__':
    path = sys.argv[1].replace('\\', '/') # Windowsify the path
    renamer(path)

Answer 1

Windows can’t rename a path that has an open file. It should work if you move the os.rename call out of the with block so that the file is closed. However, you’re repeating this for multiple files in the same path, and the directory name in path will no longer exist after you’ve renamed it. Also, os.walk can’t traverse subdirectories after you’ve renamed the parent directory.

I would check the config files while walking the tree and append (path, new_path) tuples to a list. Then I’d rename the directories in reverse order.

Also, match might be None, in which case trying to access match.group will raise an AttributeError. And Windows system calls seem to handle mixed separators fine in case you want to skip the ‘Windowsify’ step. To clean up a path for printing/logging, os.path.normpath consistently uses os.path.sep as well as resolving ‘.’ and ‘..’ in a path.