An Infinite Bag of Dice

dbag.py

import random
import re
import sys


def _roll_func(count, sides):
    def _roll():
        return sum(random.randint(1, sides) for _ in range(count))

    return _roll


class DBag:
    def __getattr__(self, name):
        if name.startswith("roll_"):
            match = re.match(r"roll_(?P<count>\d*)d(?P<sides>\d+)", name)
            if match:
                count_string = match.group("count")
                if count_string == "":
                    count = 1
                else:
                    count = int(count_string)
                sides = int(match.group("sides"))
                return _roll_func(count, sides)
        raise AttributeError(f"{__class__.__name__!r} object has no attribute {name!r}")


sys.modules["dbag"] = DBag()

exercise_dbag.py

import dbag

print(f"D6: {dbag.roll_d6()}")
print(f"3D6: {dbag.roll_3d6()}")
print(f"3D20: {dbag.roll_3d20()}")

# OMG I really didn't expect the following to work:
from dbag import roll_d6 as d6

print(f"D6 {d6()}")