*args in recursion: TypeError: unsupported operand type(s) for +: 'int' and 'tuple'

I am learning python. trying to use take *args as parameter in a recursion function (for addition of 'n' numbers), but getting error: Below is my code and error:

def add(*n):
  if len(n) == 1:
    return n[0]
  else:
    sum =  n[len(n)-1] + add(n[:-1])
  return sum  


a = add(2,4,6)
print(a)

Error:

Traceback (most recent call last):
  File "/tmp/sessions/9d1de49c52e0e9b9/main.py", line 22, in <module>
    a = add(2,4,6)
  File "/tmp/sessions/9d1de49c52e0e9b9/main.py", line 18, in add
    sum =  n[len(n)-1] + add(n[:-1])
TypeError: unsupported operand type(s) for +: 'int' and 'tuple'

please explain what i am doing wrong

Solution

I would propose a simpler setup:

def add(*n):
    if len(n) == 1:
        return n[0]
    return n[0] + add(*n[1:])    # n[1:] gives the "rest" of a list, i.e. all elements after the first.

In a function definition (def add(*n):), the star collects multiple separate arguments into a list.
e.g. when you call add(2, 4, 6), then n will be a list [2, 4, 6]
In a function call (add(*n)) the star spreads a list into multiple separate arguments.
e.g. when you have n = [2, 4, 6], then calling add(*n) will be as if you had called add(2, 4, 6)

In order to a list that to a function that collects its arguments, you need to spread it out first.

Your code did the first thing, but not the second. That's why it doesn't work:

def add(*n):                            # <-- collecting multiple arguments into a list
  if len(n) == 1:
    return n[0]
  else:
    sum =  n[len(n)-1] + add(n[:-1])    # <-- not spreading list into multiple arguments
  return sum

FWIW, an even shorter implementation would go like this

def add(*n):
    return 0 if not n else n[0] + add(*n[1:])