Summary: In this tutorial, we will learn what *args and **kwargs are in Python and why we should use them in our programs.

What is the need of *args and **kwargs?

Consider a situation where we have to write multiple functions just for the sake of accepting different numbers of arguments.

For example the following add method in Python:

def add(a, b):
    return a+b

def add(a, b, c, d, e, f):
    return a+b+c+d+e+f

print(add(5,6))                #output 11
print(add(5, 6, 1, 5, 2, 2))   #output 21

Note that we have to write two overloaded functions to add different numbers of arguments.

Every time the number of arguments differs, we need to write a specific function corresponding to the same.

One way we can resolve this is by using a list as parameter to accept multiple integers like the following:

def add(lst):
    return sum(lst)

print(add([5, 6, 1, 5, 2, 2]))   #output 21

Though this solves the problem, it still changes the way we wanted to use the function.

There is another way using which we can make a function in Python more flexible with arguments, and that is by using *args and **kwargs.

What are *args and **kwargs?

*args and **kwargs are keywords in Python which when defined as arguments allows a function to accept a varying number of arguments.

They are useful in cases when we are unsure of the number of arguments for a particular function.

Both of them make a function flexible in terms of arguments, but they slightly differ from each other. Let see examples of both.

*args in Python

*args in Python is a Non-Keyword Argument that can accept and store a variable number of positional arguments as a tuple.

A positional argument is a name that is not followed by an equal sign (=) and default value.

def add(*args):

add()                #0-arguments
add(5, 6, 4)         #3-arguments
add(1, 1, 1, 1, 1)   #5-arguments



As you can notice, *args can accept a variable number of arguments (even 0 arguments), thus makes a function more flexible.

If we would not have used *args, we would have to define separate functions for each function call.

Can we Rename *args?

Yes, we can. This is because args in *args is just a name, what is more important is the operator *.

The * in *args is an unpacking operator that transforms the incoming arguments into a Python tuple.

Keeping the * operator as it is, we can rename the args to any name like the following:

def add(*integers):
add(-1, 7, 2, 6)    #output 14

**kwargs in Python

**kwargs in Python is a Keyword Argument that can accept and store the keyword arguments of varying types as a dictionary.

A keyword argument (also known as named argument) is followed by an equal sign and an expression that gives its default value.

It is useful in cases when we want a function to accept a varying number of arguments and at the same time are also uncertain of their types.

Consider the following code, where a function accepts two different keyword arguments of varying types:

def student(name="", roll=-1):
    print(name)    #output: pencil
    print(roll)    #output: 77
student(name="pencil", roll=77)

Here, we can use **kwargs to make the function more flexible with respect to keyword arguments as follows:

def student(**kwargs):
    print(kwargs['name'])   #output: pencil
    print(kwargs['roll'])   #output: 77

student(name="pencil", roll=77, department="IT")

As you can see, we have passed an additional keyword argument (i.e. department) to the student function and yet the code works fine.

This is the power of **kwargs in Python.

Can we Rename **Kargs?

Yes likewise *args, we can rename kwargs in **kwargs.

The important part is the ** (unpacking operator) which should be prefixed with the name.

Note: we can use any names instead of args and kwargs, what makes them meaningful is * (single asterisk) to make it Non-Keyword Argument and ** (Double asterisks) to make it Keyword Argument.

Hope now you got little idea about *args and **kwargs in python and will be able to use it in your programs. Any doubts then comment below.

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