[tools] Random integer vector sum up to N

import random

'''
Let n be the number you want values to add up to.
Generate a random sample of random size (less than n), consisting of
values in the range 1 to n exclusive of n. Now add the endpoints 0 and n,
and sort. Successive differences of the sorted values will sum to n.

If you'd like to be able to specify the number of terms in the sum explicitly,
or have it be random if unspecified, add an optional argument:
'''

def random_sum_to(n, num_terms = None):
    num_terms = (num_terms or random.randint(2, n)) - 1
    a = random.sample(range(1, n), num_terms) + [0, n]
    list.sort(a)
    return [a[i+1] - a[i] for i in range(len(a) - 1)]

total = 1000
n_terms = 20
my_list = random_sum_to(total, n_terms)
print(my_list)
print(sum(my_list))