使用递归获得数字的总和

Question

design a function that accept an integer argument and returns the sum of all the integers from 1 up to the number passed as an argument.

it runs and displays the numbers up to what i entered. then i stored those values in list. won't add values in list

def main():

    #local var
    number = 0
    num_list = []

    #input number from user
    number = int(input('Enter number: '))

    print_num(number)
    print('The total value of the list is: ', sum_list(num_list))

def print_num(n):
    num_list = []
    if n > 1:
        print_num(n - 1)
        num_list.append(n)

        print(n, sep =' ')
    return num_list

def sum_list(num_list): 
    for i in range(len(num_list)):  
        if len(num_list) == 0:
             return num_list[0]
        else:
            return num_list[0] + sum_list(num_list[1:])


main()

output:

Enter number: 10
2
3
4
5
6
7
8
9
10
The total value of the list is:  None

Answer 1

You should not iterate through the length of num_list . Instead, return the sum of the first item plus the returning value of the recursive call with the rest of the items, until the list is empty, at which point return 0:

def sum_list(num_list):
    if not num_list:
        return 0
    return num_list[0] + sum_list(num_list[1:])

so that sum_list([1, 5, 4, 2]) returns: 12