convert source code files to pdf format in python

import os
import sys

def find_file(root_dir, type):
    dirs_pool = [root_dir]
    dest_pool = []

    def scan_dir(directory):
        entries = os.walk(directory)
        for root, dirs, files in entries:
            dirs_pool.extend([os.path.join(root, dir_entry) for dir_entry in dirs])
            for file_entry in files:
                if type in str(file_entry)[-len(type):]:
                    dest_pool.append(''.join(os.path.join(root, file_entry)))

    while dirs_pool:
        scan_dir(dirs_pool.pop())
    return dest_pool

def gen_ps(root_dir, type):
    vim_cmd = 'vim -me -e -c ":hardcopy >%.ps" -c ":q" '
    ps2pdf_cmd = 'ps2pdf {filename}.ps {filename}.pdf'
    dests = find_file(root_dir, type)
    if not dests:
        return
    print 'found these source code files:'
    for dest in dests:
        print dest
    print 'begin generate ps files!'
    for dest in dests:
        command = ''.join([vim_cmd, dest])
        print command
        os.system(command)
    for dest in dests:
        command = ps2pdf_cmd.format(filename=dest)
        print command
        os.system(command)

if __name__ == '__main__':
    if len(sys.argv) == 3:
        gen_ps(sys.argv[1], sys.argv[2])
    else:
        print 'usage: python code2pdf.py directory filetype
' 
              'such as: python code2pdf.py /home/bruce/python .py'