args/kwargs Python

In this post, we look at examples of the use of *args and *kwargs.

Consider a function that takes 2 positional arguments and adds them:

def sum(x, y):
    print (x + y)

sum(5, 4)
Output 9

Using *args

Can we modify the function sum() so that it can take any number of arguments? That’s the purpose of *args:

def sum(*args):
    s = 0
    for  in args:
        s += i
    print(s)

sum(4, 5)
sum(2, 3, 4)
sum(3, 5, 10, 6)

*args enables to send a argument list of variable-length in to thr function.

Using **kwargs

**kwargs (note the double asterix) is used to pass a keyworded argument dictionary of variable-length, to a function.

Let’s look at the example below:

def concat(**kwargs):
    m = ""
    for k, val in kwargs.items():
        m += val
    return m

input = {"name_1": "A", "name_2": "N", "name_3": "D", "name_4": "D", "name_5": "R", "name_6": "O", "name_7": "I", "name_8": "D"}
concat(**input)

output: "'ONDAIDDR"

Weird, we would expect the output to be ANDROID. So why are the letters shuffled like that?

The reason is that Python does not preserve the order in which the keyword arguments were passed to the function in a dictionaries: the keys may not be ordered.

With **kargs, we can pass a longer or shorter dict() to the function, and therefore there is the flexibility to use any argument length.