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1. Basic Function

def greet():
    print("Hello, World!")

greet()

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2. Function with Arguments

def greet(name):
    print(f"Hello, {name}!")

greet("Raj")

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3. Function with Default Arguments

def greet(name="World"):
    print(f"Hello, {name}!")

greet()
greet("Raj")

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4. Function with Return Statement

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

result = add(10, 5)
print(f"Addition: {result}")

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5. Function with Multiple Return Statements

def add_sub(a, b):
    return a + b, a - b

add, sub = add_sub(10, 5)
print(f"Addition: {add}, Subtraction: {sub}")

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6. Function with Keyword Arguments

def greet(name, message):
    print(f"{message}, {name}!")

greet(name="Raj", message="Good Morning")

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7. Function with Arbitrary Arguments

def greet(*names):
    for name in names:
        print(f"Hello, {name}!")

greet("Raj", "Kumar", "Bala")

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8. Function with Docstring

def greet(name):
    """
    This function greets the person passed in as a parameter
    """
    print(f"Hello, {name}!")

greet("Raj")
print(greet.__doc__)

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9. Function with Lambda

add = lambda a, b: a + b
result = add(10, 5)
print(f"Addition: {result}")

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10. Function with Recursion

def factorial(n):
    if n in (0, 1):
        return 1
    else:
        return n * factorial(n - 1)

result = factorial(5)
print(f"Factorial: {result}")

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11. Function with Global Variables

x = 10

def display():
    print(f"Value of x: {x}")

display()

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12. Function with Local Variables

def display():
    y = 20
    print(f"Value of y: {y}")

display()

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13. Function with Nonlocal Variables

def outer():
    x = 10
    def inner():
        nonlocal x
        x = 20
        print(f"Inner: {x}")
    inner()
    print(f"Outer: {x}")

outer()

Output:

Inner: 20
Outer: 20

The nonlocal keyword is used inside a nested function to modify a variable from its enclosing (non-global) scope. Without nonlocal, assigning a new value to a variable inside a nested function creates a new local variable instead of modifying the one from the outer function.

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14. Function with Global Keyword

def display():
    global z
    z = 30
    print(f"Value of z: {z}")

display()
print(f"Value of z: {z}")

Output:

Value of z: 30
Value of z: 30

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15. Function with Pass Statement

def display():
    pass

display()

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16. Function with Recursion Limit

import sys

sys.setrecursionlimit(200)

def factorial(n):
    if n in (0, 1):
        return 1
    else:
        return n * factorial(n - 1)

result = factorial(100)
print(f"Factorial: {result}")

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17. Function with Annotations

def greet(name: str) -> None:
    print(f"Hello, {name}!")

greet("Raj")
print(greet.__annotations__)

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18. Function with Annotations and Return Type

def add(a: int, b: int) -> int:
    return a + b

result = add(10, 5)
print(f"Addition: {result}")
print(add.__annotations__)

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19. Function with Annotations and Default Arguments

def greet(name: str = "World") -> None:
    print(f"Hello, {name}!")

greet()
greet("Raj")
print(greet.__annotations__)

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20. Function with Annotations and Multiple Return Statements

def add_sub(a: int, b: int) -> tuple:
    return a + b, a - b

add, sub = add_sub(10, 5)
print(f"Addition: {add}, Subtraction: {sub}")
print(add_sub.__annotations__)

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21. Function with Annotations and Keyword Arguments

def greet(name: str, message: str) -> None:
    print(f"{message}, {name}!")

greet(name="Raj", message="Good Morning")
print(greet.__annotations__)

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22. Function with Annotations and Arbitrary Arguments

def greet(*names: str) -> None:
    for name in names:
        print(f"Hello, {name}!")

greet("Raj", "Kumar", "Bala")
print(greet.__annotations__)

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23. Function with Annotations and Lambda

Lambda function does not support annotations.

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24. Function Decorators

def uppercase_decorator(function):
    def wrapper():
        result = function()
        return result.upper()
    return wrapper

def greet():
    return "Hello, World!"

greet = uppercase_decorator(greet)
print(greet())

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25. Function with Decorator Syntax

def uppercase_decorator(function):
    def wrapper():
        result = function()
        return result.upper()
    return wrapper

@uppercase_decorator
def greet():
    return "Hello, World!"

print(greet())

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26. Function with Multiple Decorators

def uppercase_decorator(function):
    def wrapper():
        result = function()
        return result.upper()
    return wrapper

def split_decorator(function):
    def wrapper():
        result = function()
        return result.split()
    return wrapper

@split_decorator
@uppercase_decorator
def greet():
    return "Hello, World!"

print(greet())

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27. Function with Arguments in Decorator

def decorator_with_args(function):
    def wrapper(*args, **kwargs):
        print("Arguments:", args, kwargs)
        result = function(*args, **kwargs)
        return result.upper()
    return wrapper

@decorator_with_args
def greet(name):
    return f"Hello, {name}!"

print(greet("Raj"))

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28. Advanced Function

def apply(func, x):
    return func(x)

def add(x):
    return x + 1

def sub(x):
    return x - 1

def square(x):
    return x * x

print(apply(add, 10))
print(apply(sub, 10))
print(apply(square, 10))

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29. Function with Nested Functions

def outer():
    def inner():
        print("Inner Function")
    inner()
    print("Outer Function")

outer()

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30. Function with Nested Functions and Closures

def outer():
    x = 10
    def inner():
        print(f"Value of x: {x}")
    return inner

inner = outer()
inner()
  • Closure Concept – inner() is a closure because it captures and retains access to x = 10 from outer() even after outer() has finished executing.
  • Function Reference – outer() returns inner without calling it, so inner becomes a function reference that can be executed later.
  • Execution Flow – Calling outer() assigns x = 10, returns inner, and when inner() is called, it prints “Value of x: 10”.
  • Variable Retention – Even though outer() is done executing, Python keeps x = 10 alive inside inner() due to the closure mechanism.
  • Encapsulation – This technique avoids global variables, keeps data within functions, and allows multiple closures to store different values.