Is this too much for new programmers already?

roll-dice.py

"""DICE ROLLER

By Al Sweigart al@inventwithpython.com

Example input:
  3d6 rolls three 6-sided dice
  1d10+2 rolls one 10-sided dice, and adds 2
  2d17-1 rolls two 17-sided dice, and subtracts 1
  QUIT quits the program
"""
import random
import sys


def main():
    print(__doc__)
    while True:
        try:
            roll_the_dice()
        except KeyboardInterrupt:
            sys.exit("bye :)")
        except Exception as exc:
            # Catch any raised exceptions and display the message to the user:
            print(
                'Invalid input. Enter something like `3d6` or `1d10+1`\n'
                'Input was invalid because: ' + str(exc)
            )
            continue


def roll_the_dice():
    diceStr = input('> ')  # The prompt to enter the dice string.
    if diceStr.upper() == 'QUIT':
        sys.exit()

    # Clean up the dice string by removing spaces, converting to lowercase:
    diceStr = diceStr.lower().replace(' ', '')

    # Find the number of dice to roll:
    dIndex = diceStr.find('d')
    if dIndex == -1:
        raise Exception('Missing the "d" character.')

    # Get the number of dice:
    numberOfDice = diceStr[:dIndex]  # The `3` in `3d6+1`.
    if not numberOfDice.isdecimal():
        raise Exception('Missing the number of dice.')
    numberOfDice = int(numberOfDice)

    # Find if there is a plus or minus sign:
    modIndex = diceStr.find('+')
    if modIndex == -1:
        modIndex = diceStr.find('-')

    # Find the number of sides:
    if modIndex == -1:
        numberOfSides = diceStr[dIndex + 1:]  # The `6` in `3d6+1`.
        if not numberOfSides.isdecimal():
            raise Exception('Missing the number of sides.')
        numberOfSides = int(numberOfSides)

        modAmount = 0
    else:
        numberOfSides = diceStr[dIndex + 1:modIndex]
        if not numberOfSides.isdecimal():
            raise Exception('Missing the number of sides.')
        numberOfSides = int(numberOfSides)

        # Find the modifier amount:
        modAmount = int(diceStr[modIndex + 1:])  # The `1` in `3d6+1`.
        if diceStr[modIndex] == '+':
            pass # Do nothing if it's +.
        elif diceStr[modIndex] == '-':
            # Change the modification amount to negative:
            modAmount = -modAmount

    # Simulate the dice rolls:
    rolls = []
    for i in range(numberOfDice):
        rolls.append(random.randint(1, numberOfSides))

    # Display the total:
    print(sum(rolls) + modAmount, '(', end='')

    # Display the individual rolls:
    for i, roll in enumerate(rolls):
        rolls[i] = str(roll)
    print(', '.join(rolls), end='')

    # Display the modifier amount:
    if modAmount != 0:
        print(', %s%s' % (diceStr[modIndex], abs(modAmount)), end='')
    print(')')


if __name__ == '__main__':
    sys.exit(main())