Functions that Accept Variable Length Key Value Pair as Arguments

To pass a variable-length key-value pair as an argument to a function, Python provides a feature called **kwargs.
kwargs stands for Keyword arguments. It proves to be an efficient solution when one wants to deal with named arguments (arguments passed with a specific name (key) along with their value) in their function.

Here's an example:

def func(**kwargs):
    for key, val in kwargs.items():
        print(key, ": ", val)

func(name="GFG", country="India")

name :  GFG
country :  India

Syntax:

def functionName(**kwargs):
# code
kwargs: it's the variable name using which we can access the arguments keys and values.

Note: adding '**' to any term makes it a kwargs parameter. It accepts keywords as arguments. 

Let's discuss some use cases of **kwargs with examples to get a better understanding.

Passing and Printing Key-Value Pairs

In this example, we define a function that accepts keyword arguments and prints them as a dictionary.

def func(**kwargs):
    print(kwargs)

func(k1 = "Geeks", k2 = "For", k3 = "Geeks")

{'k1': 'Geeks', 'k2': 'For', 'k3': 'Geeks'}

Iterating Through Keyword Arguments

We can loop through kwargs using kwargs.items() to access both the keys and values.

def func(**kwargs):
    for key, val in kwargs.items():
        print("The value of ", key," is", val)

func(short_form = "GFG", full_name="geeksforgeeks")

The value of  short_form  is GFG
The value of  full_name  is geeksforgeeks

Concatenating String Arguments

This example shows how **kwargs can be used to concatenate multiple string values passed as keyword arguments.

def func(**kwargs):
    # initialising empty string
    s = ""
    
    for ele in kwargs.values():
        s += ele
    return s

print(func(a="g", b="F", c="g"))

gFg

Multiplying Numeric Values

We can easily perform arithmetic operations over the items of argumets.

def func(**kwargs):
    ans = 1
    
    for ele in kwargs.values():
        ans *= ele
    return ans

print(func(a=1, b=2, c=3, d=4, e=5))

120

Merging Two Dictionaries

We can create a function that accepts two dictionaries as keyword arguments and merges them into one.

def func(**kwargs):
    res = {}
    
    for key, val in kwargs.items():
        res[key] = val
    return res

print(func(first={"a": 1, "b": 2}, second={"c": 3, "d": 4}))

{'first': {'a': 1, 'b': 2}, 'second': {'c': 3, 'd': 4}}

Formatting a String with Dynamic Values

Using **kwargs, we can accept multiple key-value pairs and dynamically format them into a structured string. This is particularly useful when dealing with flexible data inputs, such as logging messages, creating query strings, or displaying structured information.

def func(**kwargs):
    return " ".join([f"{key}={val}" for key, val in kwargs.items()])

print(func(name="GfG",country="India"))

name=GfG country=India

Explanation:

• accessing key-value data using for key, value in kwargs.items().
• " ".join(formatted_pairs) combines the formatted key-value pairs into a single string, separated by spaces.