RPG dice roller

dice.py

import random
import re
import sys

def roll(dices=1, sides=20, modifier=0):
    troll = sum(random.randint(1, sides) for dice in range(dices)) + modifier
    return troll

def main():
    dice_pattern = re.compile(r'(\d*)d(\d*)([+-]?\d*)')
    dices = sys.argv[1:]
    if not dices:
        print(f'1d20: {roll()}')
    elif len(dices) == 1:
        d = dice_pattern.match(dices[0])
        droll = roll(int(d.group(1) or 1), int(d.group(2)), int(d.group(3) or 0))
        print(f'{d.group(1) or 1}d{d.group(2)}{d.group(3)}: {droll}')
    else:
        troll = 0
        for dice in dices:
            d = dice_pattern.match(dice)
            droll = roll(int(d.group(1) or 1), int(d.group(2)), int(d.group(3) or 0))
            print(f'{d.group(1) or 1}d{d.group(2)}{d.group(3)}: {droll}')
            troll += droll
        print(f'Total: {troll}')

if __name__ == '__main__':
    main()