Problem opening files while using os.path.walk

[R. Arens]

Hi. I'm writing what should be a simple function that will walk a
directory structure, opening and joining all files within the
directory tree into a single huge file. I'm using os.path.walk and
testing the list of files returned to the function specified in walk
to make sure that each file is actually a file as opposed to another
directory - herein lies the problem. The function isn't seeing
_anything_ as a file, and is just skipping it. This one has me quite
perplexed, and I'd appreciate any help anyone can offer. Thanks!

Code follows....

import os, sys

def walkJoin(out, dirname, names):
    print "Current directory: " + dirname
    names.sort()
    for name in names:
        if os.path.isfile(name):
            file = open(name, 'r')
            lines = file.readlines()
            for line in lines:
                out.writeline(line)
            file.close()
        else:
            print "Keep walking"
            os.path.walk(name, walkJoin, out)
    print "Done with directory ", name

def main():
    out = open('out.txt', 'w')
    directory = raw_input("Enter the name of the directory: ")
    print "Root directory " + directory
    os.path.walk(directory, walkJoin, out)
    out.close()