dice.py

#!/usr/bin/python3
import argparse, random, sys

argparser = argparse.ArgumentParser()
argparser.add_argument('die', default='1d6')
argparser.add_argument('-n', '--count', type=int, default=1)
args = argparser.parse_args()

def parse_die(die):
    if 'd' in die:
        number, sides = map(int, die.split('d', 1))
    else:
       number = int(die)
       sides = 6
    return number, sides

try:
    number, sides = parse_die(args.die)
except ValueError:
    sys.exit('Invalid die: \'{0}\''.format(args.die))

die = '{0}d{1}'.format(number, sides)

for i in range(args.count):
    rolls = [random.randrange(sides)+1 for j in range(number)]
    print('{0}: {1} = {2}'.format(die, '+'.join(map(str,rolls)), sum(rolls)))