To start exploring variable argument lengths in Python functions, let’s take a look at a familiar function we have been using for a long time:
Notice how the print() function does not care how many arguments we pass to it. It has no expectation that we are going to pass in one argument or even a million! So the question is, how does print() accomplish this?
Well, in Python, there is an additional operator called the unpacking operator (*). The unpacking operator allows us to give our functions a variable number of arguments by performing what’s known as positional argument packing.
Let’s explore how it works by examining a basic function that utilizes the unpacking operator:
If we called this function with random arguments:
Our output would show us what is inside of *args:
Notice two things:
In our
print()call, we simply use the name ofargswith the unpacking operator omitted. The name ofargsis completely arbitrary, and this example works just the same:def my_function(*randomname): print(randomname)Whatever name follows the unpacking operator (*) will store the arguments passed into the function in the form of a tuple. This allows our functions to accept any number of arguments just like the
print()function we examined earlier. In this case,argshas three values inside, but it can have many more (or fewer).
Let’s practice using the unpacking operator for positional arguments in a function!
Instructions
Jiho wants to expand our restaurant application to also take orders from customers. This is the perfect time to use the unpacking operator since we never know how many items customers are going to order.
To start, we want to build a function that will compile a list of all the items a customer wants to order and then print it out. This will help our kitchen know what to cook.
Define a function called print_order() that will take in a variable number of arguments using a parameter called order_items. The function should simply print order_items.
Looks like our first order came in! Call our function print_order() with the following order items:
'Orange Juice''Apple Juice''Scrambled Eggs''Pancakes'