dice2.py

import random

# dice - simulate dungeon & dragons dice to generate random values



def diceroll(dicestring):
    """
    lower d for dice rolls without re-roll
    1d6 -> rolls one six-sided die 
    2d6 -> rolls two six-sided dice
    1d20+5 -> rolls one twenty-sided die and adds 5 to the end result
    
    uppercase D for reroll (count as (sides-1))
    
    1D6 -> roll a 6-sided die with re-rolling:
           when a 6 is rolled it count as 5 but a re-roll is done.
           
    2D6 ->   roll two 6-sided dice with re-rolling
    2D6-2 -> roll two 6-sided dice with re-rolling 
             and subtract 2 of the end result
    """
    reroll = False
    if dicestring.lower().count("d") != 1:
        raise ValueError("more or less than one 'd' ('D') in dicestring")
    if "D" in dicestring:
        reroll = True
    left, right = dicestring.lower().split("d")
    number_of_dice = int(left)
    if ("+" in right) or ("-" in right):
        sign = "+" if "+" in right else "-"
        sides, delta = right.split(sign)
        sides = int(sides)
        delta = int(delta)
        if sign == "-":
            delta = -delta
    else:
        delta = 0
        sides = int(right)
    text = dicestring+": "
    result = 0
    for d in range(number_of_dice):
        if reroll:
            roll = 0
            while True:
                temp = random.randint(1,sides)
                if temp == sides:
                    roll += temp -1
                else:
                    roll += temp
                    break
        else:
            roll = random.randint(1, sides)
        result += roll
        if d > 0:
            text+=f"+{roll}"
        else:
            text+= f"{roll}"
        if reroll and (roll > sides):
            text += "!"
    result += delta
    if delta != 0:
        if delta > 0:
            text += f"+{delta}={result}"
        else:
            text += f"{delta}={result}"
    return result, text
    
if __name__ == "__main__":
    # testing
    for _ in range(100):
        print(diceroll("1D20"))