Recursion does not work with positional arguments

Question

I am trying to do multiplication recursion (multiplying all the values of a container) in Python. The function receives the elements of the list as positional argument(*n). On execution I receive the error saying "Maximum recursion depth reached". However, the code works fine if I simply use n instead of *n and send the elements in a list.

Code not working:

def multiply(*n):
    if n:       
        return n[0]*multiply(n[1:])
    else:
        return 1

multiply(5,1,4,9)

Working code:

def multiply(n):
    if n:       
        return n[0]*multiply(n[1:])
    else:
        return 1

multiply([5,1,4,9])

Answer 1

In the first piece of code, the expression

multiply(n[1:])

is calling multiply with only one argument. Namely, the rest of the list. In order to call it with arguments equal to the contents of the list n[1:], you use the splat operator again, like so:

multiply(*n[1:])

Answer 2

When you tell a function to expect an arbitrary number of positional arguments with *n, you need to accommodate it in that format: with multiple arguments, not with a single iterable that contains all the arguments. If you have a single iterable whose elements should be used as arguments, you have to unpack it with * when you call it. The second function works because it's expecting a single, iterable argument, and you send it a single, iterable argument.

Replace n[1:] with *n[1:].