Expansions of a natural number into sums

expansions.py

def get_expansions(num, nterms):
    result = []
    
    def run(cur_sum, cur_vals, remain):
        if remain == 0:
            if cur_sum == num:
                result.append(tuple(cur_vals))
                return
        elif remain == 1:
            cur_vals.append(num - cur_sum)
            run(num, cur_vals, 0)
            cur_vals.pop()
        else:
            for term in xrange(1, num - cur_sum):
                cur_vals.append(term)
                run(cur_sum + term, cur_vals, remain - 1)
                cur_vals.pop()

    run(0, [], nterms)
    return result