Accepting a variable number of arguments

The built-in function max can accept an arbitrary number of arguments:

print(max(1))  # 1
print(max(1, 2))  # 2
print(max(1, 2, 3))  # 3
print(max(1, 2, 3, 4))  # 4
...

There are other built-ins that do that… But you can also write functions that behave in this way.

In Python, for a function to accept a number of arbitrary arguments, you just add an asterisk * to the left of the parameter that represents the “arbitrary number of arguments” that the user might pass in. Usually, in the Python world, we call it *args (pronounced “star args”).

The parameter that gets the asterisk * next to it will then be a tuple with whatever values the user passed in. Here is an example of a function that accepts a variable number of arguments and whose only functionality is printing those same arguments:

def print_star_args(*args):
    print(args)

If you use the function print_star_args with a couple of different arguments, you will see that the variable args is always a tuple:

print_star_args()  # ()
print_star_args(True)  # (True,)
print_star_args(1, 2, 3)  # (1, 2, 3)

*args can also be used after some positional arguments, in which case the function accepts as many positional arguments as specified, plus an arbitrary number of arguments. For example, the function add_two_or_more shown below accepts two mandatory positional arguments, plus as many arguments as you want. But the minimum number of arguments that are accepted is two:

def add_two_or_more(a, b, *args):
    return a + b + sum(args)

print(add_two_or_more(1, 2))  # 3
print(add_two_or_more(1, 2, 3, 4, 5, 6))  # 21

As a quick comprehension check, can you implement a function my_max that accepts a variable number of arguments and then returns the maximum value? If you do it right, the snippet of code below should work:

print(my_max(1))  # 1
print(my_max(1, 2))  # 2
print(my_max(1, 2, 3))  # 3
print(my_max(1, 2, 3, 4))  # 4