What is the difference between *args and **kwargs?

In Python, *args and **kwargs are special syntax used in function definitions to allow for variable-length arguments. Here’s the detailed difference:

---

1. *args (Non-Keyword Arguments)

• Purpose: *args is used to pass a variable number of positional arguments to a function.
• How it Works: Inside the function, *args is treated as a tuple containing all the additional positional arguments passed.

Example:

def example_function(*args):
    for arg in args:
        print(arg)

example_function(1, 2, 3, 4)
# Output:
# 1
# 2
# 3
# 4

• Key Points:
  • Use *args when the number of arguments is unknown and you don’t need to associate names with values.
  • It collects all extra positional arguments into a tuple.

---

2. **kwargs (Keyword Arguments)

• Purpose: **kwargs is used to pass a variable number of keyword arguments (name-value pairs) to a function.
• How it Works: Inside the function, **kwargs is treated as a dictionary containing all the additional keyword arguments passed.

Example:

def example_function(**kwargs):
    for key, value in kwargs.items():
        print(f"{key} = {value}")

example_function(a=1, b=2, c=3)
# Output:
# a = 1
# b = 2
# c = 3

• Key Points:
  • Use **kwargs when you need to handle named arguments that you may not know in advance.
  • It collects all extra keyword arguments into a dictionary.

---

3. Using *args and **kwargs Together

• Order: If you use both *args and **kwargs in the same function definition, *args must appear before **kwargs.

Example:

def example_function(*args, **kwargs):
    print("Positional arguments:", args)
    print("Keyword arguments:", kwargs)

example_function(1, 2, 3, a=4, b=5)
# Output:
# Positional arguments: (1, 2, 3)
# Keyword arguments: {'a': 4, 'b': 5}

---

4. Practical Use Case

When the exact number and type of arguments are unknown:

• *args can capture extra positional arguments.
• **kwargs can capture extra named arguments.

def greet(*args, **kwargs):
    for name in args:
        print(f"Hello, {name}!")
    for key, value in kwargs.items():
        print(f"{key}: {value}")

greet("Alice", "Bob", age=30, location="New York")
# Output:
# Hello, Alice!
# Hello, Bob!
# age: 30
# location: New York

---

5. Summary

Feature	*args	**kwargs
Purpose	Handles extra positional arguments	Handles extra keyword arguments
Data Type	Tuple	Dictionary
Use Case	For a variable number of arguments without names	For a variable number of arguments with names
Example Input	function(1, 2, 3)	function(a=1, b=2, c=3)

By combining *args and **kwargs, you can write functions that are highly flexible and capable of handling a wide range of inputs.