#!/usr/bin/env python

import os
import sys
import shutil

def rename(root, name, replace):
    src = os.path.join(root, name)
    dest = os.path.join(root, name.replace(" ", replace))
    if filename.find(" ") != -1: 
        try:    
            os.rename(src, dest)
        except OSError:
            print "%s: ERROR: Permission Denied: %s" % (sys.argv[0], src)
            sys.exit(1)

if __name__ == "__main__":
    if len(sys.argv) != 3:
        print "%s <dir> <replacement>" % (sys.argv[0])
        sys.exit(1)

    dir = os.path.abspath(sys.argv[1])
    replace = sys.argv[2]

    if not os.path.isdir(dir):
        print "%s: The first argument needs to be a directory" % (sys.argv[0])

    for dirpath, dirnames, filenames in os.walk(dir, topdown=False): 
        for filename in filenames:
            rename(dirpath, filename, replace)

        for dirname in dirnames:
            rename(dirpath, dirname, replace)