Simple loop command

loop

#!/usr/bin/env python
from __future__ import print_function
import argparse
import subprocess
import sys

parser = argparse.ArgumentParser(
    prog='loop',
    formatter_class=argparse.ArgumentDefaultsHelpFormatter
)
parser.add_argument('-v', '--verbose', action='store_true')
parser.add_argument(
    '-A', '--start',
    type=int,
    default=0,
    metavar='num',
    help="$SUB will be substituted for loop number",
)
parser.add_argument('-I', default='%%', dest='sub', help='substitution string')
parser.add_argument('times', type=int)
parser.add_argument('command', nargs='+')
opts = parser.parse_args()

command = ' '.join(opts.command) + '\n'
stop = opts.times + opts.start
for i in range(opts.start, stop):
    p = subprocess.Popen(['bash', '--login'], stdin=subprocess.PIPE)
    cmd = command.replace(opts.sub, str(i))
    if opts.verbose:
        print('>' + cmd, end='')
    p.stdin.write(cmd)
    p.stdin.flush()
    p.stdin.write('exit\n')
    p.wait()
    if p.returncode != 0:
        it = str(i - opts.start + 1)
        ending = {
            '1': 'st',
            '2': 'nd',
        }.get(it[-1], 'th')
        print('{}{} iteration failed'.format(it, ending))
        sys.exit(p.returncode)