How to set the data type of a function parameter in python?

Question

def recursiveSum(lst):
    if len(lst) == 0:
        return 0
    else:
        #print(str(type(lst))+'\n')    
        num = lst[len(lst)-1]
        return recursiveSum(lst.pop()) + num


size = int(input("How many number do you want to enter? = "))
lst=[]
for i in range(size):
    lst.append(input("Enter number "+str(i+1)+" = " ))
print(recursiveSum(lst))

In this code i am trying to find sum of list of numbers recursively, this is my first attempt with recursions, i think my approach and algorithm was correct, the list when passed to the recursiveSum() function somehow makes it string in the else part, the commented line when executed ends up printing

class 'list'

class 'str'

I don't understand how the print statement prints both list and str .

Can someone explain this?

Answer 1

I think you forgot to type cast to int when input:

lst.append(int(input("Enter number "+str(i+1)+" = " )))

Answer 2

Two problems:

• you do not convert your inputs into numerics/integers
• you recurse using the popped element not the remaining list

Fix:

def recursiveSum(lst):
    if len(lst) == 0:
        return 0
    else:
        num = lst[0]   # use the first one 
        return recursiveSum(lst[1:]) + num   # and recurse on the remaining slice


size = int(input("How many number do you want to enter? = "))
lst=[]
for i in range(size):
    lst.append(int(input("Enter number "+str(i+1)+" = " )))
print(recursiveSum(lst))

list.pop() returns the element popped from the list - not the list-remainder.