pad_file_names_with zeros.py

#!/usr/bin/env python3
import argparse
import os

ap = argparse.ArgumentParser(os.path.basename(__file__),
                             description=__doc__,
                             formatter_class=argparse.
                             ArgumentDefaultsHelpFormatter)
ap.add_argument('path_to_files', type=str, help='Path to files')
ap.add_argument('-z', '--zeros', type=int, default=4,
                help='Number of zeros')


if __name__ == '__main__':
    args = ap.parse_args()
    path = args.path_to_files
    files = os.listdir(path)

    for f in files:
        name, ext = os.path.splitext(f)
        pref, num = name.split()
        new_num = num.zfill(args.zeros)
        new_name = '{}_{}{}'.format(pref, new_num, ext)
        os.rename(os.path.join(path, f), 
                  os.path.join(path, new_name))
        print('Renamed {} to {}'.format(os.path.join(path, f), 
                                        os.path.join(path, new_name)))