In Python, both *args and **kwargs mean that a function can accept any number of arguments.

• *args refer to regular arguments (e.g. myFun(1,2,3)).
• **kwargs refer to keyword arguments (e.g. myFun(name="Charlie")).

Today, you will learn how you can implement functions that can accept any number of arguments/keyword arguments.

Args in Python

Let’s create a function called mySum that accepts any number of arguments and sums them up:

def mySum(*args):
    s = 0
    for num in args:
        s += num
    return s
mySum(1,2)        # returns 3
mySum(1,2,2,3,4)  # returns 12

Notice how *args are looped just like a list of numbers. This is because *args is a list of number arguments. So you could actually pass a list to mySum as well:

numbers = [1,2,3]
mySum(*numbers) # returns 6

It is really that simple. Next, let’s take a look at **kwargs.

Kwargs in Python

You can use **kwargs to pass any number of keyword arguments to a function. A keyword argument is just an argument that has a name (e.g. myFun(name="Jack")).

As an example, let’s create a function that prints some items:

def read(**kwargs):
    for key, value in kwargs.items():
        print("{}: {}".format(key, value))
read(shoes="Adidas", shirt="H&M")
read(socks="Nike")

Output:

shoes: Adidas
shirt: H&M
socks: Nike

Notice how **kwargs is looped through just like a dictionary. This is because **kwargs actually is a dictionary. This means you could pass a dictionary of items to the read function:

clothes = {"shoes": "Adidas", "shirt": "H&M"}
read(**clothes)

Output:

shoes: Adidas
shirt: H&M

Now you know how to work with *args and **kwargs. Next, let’s use both in the same function.

Use Both Args and Kwargs

Finally, you can easily mix things up and use args and *kwargs in the same function. For example:

def read_all(*args, **kwargs):
    for value in args:
        print(value)
    for key, value in kwargs.items():
        print("{}: {}".format(key, value))

# prints all the numbers and clothes passed to read_all function:
read_all(1,2,3,shirt="H&M",socks="Nike")

Naming Convention

Now that you understand *args and **kwargs, it is a good time to point out that there is nothing special about the words args and kwargs. The naming is actually up to you: *args could just as well be named *numbers. **kwargs could just as well be named **items.

All you need is to make sure to use * when dealing with regular arguments and ** when dealing with keyword arguments.

Conclusion

In Python, you can pass any number of arguments to a function by using *args or **kwargs.

• Use *args when dealing with regular arguments. Defining myFun(*args) makes it possible to call e.g. myFun(1,2) or myFun(10,1,38,7,10,2).
• Use **kwargs when dealing with keyword arguments. Defining myFun(**kwargs) makes it possible to call for example myFun(name="Jim") or myFun(socks="Nike", shirt="H&M").

Notice that *args and **kwargs can actually be named whatever you like. Remember to use * with regular arguments and ** with keyword arguments.

Thanks for reading. I hope you found this useful. Happy coding!