How to use *args And **kwargs In Python¶

usage of * args and **kwargs in functions¶

Python programming language is a simple and powerful language. It provides simple syntax with powerfull features. In this article we will discuss how to use *args and **kwargs in python. *args and **kwargs are magic powers of python. we use *args for unpacking of arguments and **kwargs for unpacking of keyword arguments.

Note: We can use *arguments instead *args and **keywordargs instead **kwargs, we can use any name in place of "args", "kwargs". Most developers use it as *args and **kwargs.

Example of python *args and **kwargs¶

def print_recieved_data(num1, num2, *args, **kwargs):
  print("num1 = ", num1)
  print("num2 = ", num2)
  print("*args = ", args)
  print("**kwargs = ", kwargs)

# case 1
print_recieved_data(10, 20)
# Output:
num1 = 10
num2 = 20
*args = ()
**kwargs = {}

# case 2
print_recieved_data(10, 20, 30, 40, name="Anji", age=23)
# Output:
num1 = 10
num2 = 20
*args = (30, 40)
**kwargs = {"name": "Anji", "age": 23}

def f1(a, b, c, d):
  return a+b+c+d
def f2(*args, **kwargs):
  return f1(*args, **kwargs)

# case3
sum = f2(1,3,4, d=100)
print sum
# Output: 108

In above code case1¶

• default values for *args are empty tuple and for **kwargs are empty dictionary.
• *args and **kwargs are not mandatory
• we can use tuple functionalities on "args" and dict functinalities on "kwargs".

In above code case2¶

• All extra arguments are stored in "args" in a tuple format.
• All key, value arguments are stored in "kwargs" in a dict format.

In above code case3¶

• when we use *args, **kwargs in function "f1(*args, **kwargs)" arguments are unpacked from the tuple and dictionary f1(*args, **kwargs) = "f1(1,3,4, d=100)"

When to use python *args and **kwargs ?

It is useful when number of parameters in a function are unknown

Example usage of python *args and **kwargs in classes¶

class Parent(object):
  def __init__(self, a, b):
    # do something
    print(a, b)

class Child(Parent):
  def __init__(self, *args, **kwargs):
    # do something
    super(Parent, self).__init__(*args, **kwargs)
    # do something

Note: Data type of *args is tuple and Data type of **kwargs in dictionary.

References: 1. https://docs.python.org/2/faq/programming.html#id15

Related Blog Articles

Basic Understanding Of Class In Python

A class is a basic design or a plan to an object. Class explains about the properties and behavior of an object.

Python Staticmethod, Classmethod And Instancemethod

We have three types of class based methods in python. They are 1.static method, 2.class method and 3.instance method. When we are working with classes we will have to deal with different types of scenarios. Based on the scenario we have to use the one of the method types. Let's get started with these python methods.

Python Working With Functions

In python functions are used to provide the same type of functionality for different inputs. Functions are mostly used for code re-usability.