A renaming script that I use to rename photos, rendered animation, or video frames. Warning, this script will rename your files! There is no undo. Use with care. Constructive comments about Python usage very welcome.

Will work on Unix-like operating systems, not sure about Windows.

# Python renamer script: creates a function called pyrename(). pyrename() will rename all files in a given folder.
# Usage: Put all the files you want to rename in an isolated folder. The function can be called by typing pyrename().
# Warning, this script will rename your files. There is no undo. Use with care.
def pyrename():
    'Put all the files you want to rename in an isolated folder. The function can be called by typing pyrename().'
    import os

    #function to ignore the hidden . files in a directory. Note the use of the 'yield' keyword
    def listdir_nohidden(path):
        for f in os.listdir(path):
            if not f.startswith('.'):
                yield f

    path = raw_input('path to folder?: ')
    #get the files from the folder and put the filenames in a list called files
    theFiles  = listdir_nohidden(path)
    files = []
    for f in theFiles:
        files.append(f)

    #user supplied values
    print 'Want to replace a character or string in your file names?'
    want_to_replace = raw_input('Type y or n. Or to completely rename type w: ')
    if want_to_replace == 'y':
        replace = raw_input('Type the character or string that you want to replace (FYI can be a space!): ')
        replace_with = raw_input('Type the character or string that you want to replace with: ')
    elif want_to_replace == 'w':
        replace = ''
        replace_with = raw_input('Type new name: ')
    else:
        replace = ''
        replace_with = ''   

    if want_to_replace != 'w':
        want_numbers = raw_input('Want your files numbered? type y or n: ')
        if want_numbers == 'y':
            zeros = raw_input('Type the amount of padding zeros you need (using a single integer, like 4): ')
        else:
            zeros = 0

    if want_to_replace == 'w':
        zeros = raw_input('Type the amount of padding zeros you need (using a single integer, like "4"): ')

    ext = raw_input('Please type the three letter extension you want to use ex: jpg (NOT the .): ')

    #remove extension, put the filenames in a list called names
    names = []
    for f in files:
        if f[-4] == '.':
            names.append(f.replace(f[-4:], ''))
        else:
            names.append(f)

    #add new names, add user supplied extension, put the filenames in a list called namesPlusEx
    namesPlusEx = []
    count = 0
    for f in names:
        if want_to_replace == 'w':
            namesPlusEx.append(f.replace(f, replace_with)+ (('.%.')+zeros+('d'))% count +'.'+ ext)
        elif want_to_replace != 'w' and want_numbers == 'y':
            namesPlusEx.append(f.replace(replace, replace_with)+ (('.%.')+zeros+('d'))% count +'.'+ ext)
        else:
            namesPlusEx.append(f.replace(replace, replace_with)+'.'+ ext)
        count += 1

    #rename the actual files
    c=0
    for f in files:
        os.rename(path+'/'+f, path+'/'+namesPlusEx[c])
        c+=1

    print 'You have re-named %d files' % len(files)

rename.py