Roll a die with optional weighted side and specified weight

script.py

import random


def is_int(x):
    '''
    Given a number, returns a boolean declaring if
    the number is an integer.
    '''

    return x % 1 == 0


def roll_die(n_sides, n_weighted=None, weight=None):
    '''
    Given number of sides to the die, the (optional) side that is weighted,
    and the weight of that side, returns the roll.
    '''

    if n_weighted is None and weight is not None:
        raise ValueError('Must specify a side to weigh if providing a weight.')

    if n_weighted > n_sides:
        raise ValueError('The weighted side must be <= the number of sides on the die.')

    if n_sides < 1 or n_weighted < 1 and n_weighted is not None:
        raise ValueError('Die values must be greater than 0.')

    if not is_int(n_sides) or not is_int(n_weighted) or not is_int(weight):
        raise ValueError('All values must be integers.')


    if weight is None:
        weight = n_sides

    if weight == 1:
        numbers = [n_weighted]

    elif weight < 1:
        numbers = [n for n in range(1, n_sides+1) if n is not n_weighted]

    elif n_weighted == None:
        numbers = [n for n in range(1, n_sides+1)]

    else:
        dist = n_sides - 1
        numbers = sum([[n] * (weight-1) + [n_weighted] for n in range(1, n_sides+1) if n is not n_weighted], [])


    # Debugging
    # print("With {} being rolled every 1/{} rolls, the numbers to choose from are \n{}\n".format(n_weighted, weight, numbers))

    roll = random.choice(numbers)
    print(roll)