*args and **kwargs in Python (Flexible Function Arguments)

Python provides special syntax to allow functions to accept variable numbers of arguments:

• *args → variable positional arguments
• **kwargs → variable keyword arguments

These are widely used in: - APIs - Decorators - Libraries - Frameworks (like Django, Flask)

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1. *args (Variable Positional Arguments)

*args allows a function to accept any number of positional arguments.

Example:

def add(*args):
    print(args)

add(1, 2, 3, 4)

Output:

(1, 2, 3, 4)

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Real World Example

A billing system where items are added dynamically:

def total_bill(*items):
    return sum(items)

print(total_bill(100, 200, 300))

Output:

600

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How *args works (Graph)

function(*args)
      |
      +--> collects all positional values
      |
      +--> stores as tuple

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Common Mistake

def test(args):
    print(args)

test(1, 2, 3)

Problem: - Only accepts one argument, not multiple

Correct:

def test(*args):

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Homework 1

Create a function that prints all numbers passed using *args.

Solution:

def show_numbers(*args):
    for num in args:
        print(num)

show_numbers(10, 20, 30)

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2. **kwargs (Variable Keyword Arguments)

**kwargs allows passing named arguments dynamically.

Example:

def show_info(**kwargs):
    print(kwargs)

show_info(name="John", age=25)

Output:

{'name': 'John', 'age': 25}

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Real World Example

User profile system:

def profile(**details):
    for key, value in details.items():
        print(key, value)

profile(name="Alice", role="Admin", active=True)

Output:

name Alice
role Admin
active True

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Graph (Flow)

function(**kwargs)
      |
      +--> collects named arguments
      |
      +--> stores as dictionary

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Common Mistake

def test(kwargs):
    print(kwargs)

test(name="John")

Problem: - Not using **kwargs, so multiple keyword args fail

Correct:

def test(**kwargs):

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Homework 2

Create a function that prints key-value pairs using **kwargs.

Solution:

def show_data(**kwargs):
    for k, v in kwargs.items():
        print(k, v)

show_data(city="Delhi", country="India")

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3. Using *args and **kwargs Together

You can combine both in one function.

Example:

def demo(*args, **kwargs):
    print("args:", args)
    print("kwargs:", kwargs)

demo(1, 2, 3, name="John", age=30)

Output:

args: (1, 2, 3)
kwargs: {'name': 'John', 'age': 30}

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Real World Example

Order system:

def order(*items, **details):
    print("Items:", items)
    print("Details:", details)

order("Pizza", "Burger", table=5, paid=True)

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Argument Order Rule

Order	Rule
1	normal arguments
2	*args
3	default arguments
4	**kwargs

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Graph

function(a, b, *args, **kwargs)

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Homework 3

Create a function that accepts: - any number of items - customer name and order ID

Solution:

def shop(*items, **info):
    print(items)
    print(info)

shop("apple", "banana", name="Ravi", order_id=101)

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4. *args and **kwargs in Decorators

Decorators use *args and **kwargs to handle flexible functions.

Example:

def decorator(func):
    def wrapper(*args, **kwargs):
        print("Before function")
        result = func(*args, **kwargs)
        print("After function")
        return result
    return wrapper

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Decorator Usage

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

print(add(5, 10))

Output:

Before function
After function
15

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Real World Example

Logging system:

def logger(func):
    def wrapper(*args, **kwargs):
        print("Calling:", func.__name__)
        return func(*args, **kwargs)
    return wrapper

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Graph (Decorator Flow)

function(a, b)
     |
     v
wrapper(*args, **kwargs)
     |
     v
original function

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Common Mistake

def wrapper():
    return func()

Problem: - Cannot handle arguments

Correct:

def wrapper(*args, **kwargs):

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Homework 4

Create a decorator that prints function name and arguments.

Solution:

def debug(func):
    def wrapper(*args, **kwargs):
        print("Function:", func.__name__)
        print("Args:", args)
        print("Kwargs:", kwargs)
        return func(*args, **kwargs)
    return wrapper

@debug
def multiply(a, b):
    return a * b

multiply(4, 5)

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Summary Table

Concept	Meaning
*args	variable positional arguments (tuple)
**kwargs	variable keyword arguments (dict)
combined	flexible function design

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Real World Mapping

Feature	Example
*args	shopping cart items
**kwargs	user profile data
decorators	logging/auth systems

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Visual Summary

*args   → (1, 2, 3)
**kwargs → {'a':1, 'b':2}

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Next Advanced Topics

• Closures (deep dive)
• Decorators chaining
• Generators (yield)
• Iterators protocol
• Context managers (with statement)
• functools module (partial, lru_cache)
• Async programming (async/await) ```