# args and kwargs in Python

Oct 10, 2022·

## Introduction

In this article, we'll discuss `*args` and `**kwargs` in Python with their uses and examples.

When writing a function, we often need to pass values to the function. These values are called function arguments.

## Problem with Function Arguments

Let us define a function to add two numbers in Python. We'll write it as:

``````def add(x,y):
return x+y

``````

Output:

``````5
``````

What if further it is required to add three numbers? Simple, we can modify the function to accept three arguments and return their sum as:

``````def add(x, y, z):
return x+y+z

``````

Output:

``````10
``````

Wasn't that quite simple? Yes, it was!

But what if we're again required to add two numbers only? Will our modified function help us get the sum? Let's see:

``````def add(x, y, z):
return x+y+z

``````

Output:

``````Traceback (most recent call last):
File "D:\Quarantine\Test\Blog-Codes\args-kwargs\main.py", line 14, in <module>
TypeError: add() missing 1 required positional argument: 'z'
``````

You see the problem?

The problem arises when we have a variable number of arguments. Shall we keep modifying the function to accept the exact number of arguments? Of course not, we won't be doing this.

Thus, there must be some other way to do it. This is where `*args` and `**kwargs` jump in!

`*args` and `**kwargs` are used as arguments of a function when we are unsure about the number of arguments to pass in the functions.

## `*args` in Python

`*args` allows us to pass a variable number of non-keyword arguments to a Python function. In the function, we should use an asterisk(`*`) before the parameter name to pass a variable number of arguments.

``````def add(*args):
print(args, type(args))

``````

Output:

``````(2, 3) <class 'tuple'>
``````

Thus, we're sure that these passed arguments make a tuple inside the function with the same name as the parameter excluding `*`.

Now let us rewrite our `add()` function with a variable number of arguments.

``````def add(*numbers):
total = 0
for num in numbers:
total += num

``````

Output:

``````5
10
17
26
``````

Note that the name of the argument need not necessarily be `args`, it can be anything, in this case, it's `numbers`. But it's generally a standard way to use `*args` as the name.

## `kwargs` in Python

`kwargs` allows us to pass a variable number of keyword arguments to a Python function. In the function, we use the double-asterisk (``)before the parameter name to denote this type of argument.

``````def total_fruits(**kwargs):
print(kwargs, type(kwargs))

total_fruits(banana=5, mango=7, apple=8)
``````

Output:

``````{'banana': 5, 'mango': 7, 'apple': 8} <class 'dict'>
``````

Thus we see that the arguments, in this case, are passed as a dictionary and these arguments make a dictionary inside the function with name same as the parameter excluding ``.

Now, let us complete the `total_fruits()` function to return the total number of fruits.

``````def total_fruits(**fruits):
total = 0
for amount in fruits.values():
total += amount

print(total_fruits(banana=5, mango=7, apple=8))
print(total_fruits(banana=5, mango=7, apple=8, oranges=10))
print(total_fruits(banana=5, mango=7))
``````

Output:

``````20
30
12
``````

Note that the name of the argument need not necessarily be `kwargs`, it can be anything, in this case, it's `fruits`. But it's generally a standard way to use `**kwargs` as the name.

## Conclusion

In this blog, we learned about two special keywords in Python - `*args` and `**kwargs` that make a Python function flexible to accept a variable number of arguments and keyword arguments respectively.