"""

Python language functions demo: args, kwargs, defaults, closures,

higher-order functions, and lambdas.

Run this file to see practical examples and output.

"""

from typing import Any, Callable, Dict, Iterable, Tuple

# Function definitions with various argument types and a simple decorator.

def positional_and_keyword(a: int, b: int = 10, *, c: int = 20) -> int:

"""Demonstrate positional args, default values, and keyword-only args."""

return a + b + c

# Variadic arguments: *args for positional, **kwargs for keyword

def varargs_example(*args: int, **kwargs: int) -> Tuple[int, Dict[str, int]]:

"""Collect arbitrary positional and keyword arguments."""

total = sum(args)

return total, kwargs

# Higher-order function: takes a callable and applies it to values

def apply_operation(values: Iterable[int], operation: Callable[[int], int]) -> list[int]:

"""Higher-order function: applies a callable to each item."""

return [operation(value) for value in values]

# Closure example: make_multiplier returns a function that multiplies by a factor

def make_multiplier(factor: int) -> Callable[[int], int]:

"""Closure example: returns a function that multiplies by factor."""

def multiplier(n: int) -> int:

return n * factor

return multiplier

# Decorator example: a simple wrapper that prints before and after calling a function

def decorator_example(func: Callable[..., Any]) -> Callable[..., Any]:

"""Simple decorator that prints before and after calling func."""

def wrapper(*args: Any, **kwargs: Any) -> Any:

print(f'Calling {func.__name__} with {args} and {kwargs}')

result = func(*args, **kwargs)

print(f'{func.__name__} returned {result}')

return result

return wrapper

# Example of a decorated function

@decorator_example

def decorated_add(a: int, b: int) -> int:

return a + b

# Lambda examples: anonymous functions for simple operations

def lambda_examples() -> list[int]:

values = [1, 2, 3, 4, 5]

squared = list(map(lambda x: x * x, values))

evens = [x for x in values if (lambda y: y % 2 == 0)(x)]

return squared + evens

def run_demo() -> None:

print('positional_and_keyword(5):', positional_and_keyword(5))

print('positional_and_keyword(5, 7, c=3):', positional_and_keyword(5, 7, c=3))

total, kwargs = varargs_example(1, 2, 3, alpha=100, beta=200)

print('varargs_example total:', total)

print('varargs_example kwargs:', kwargs)

double = make_multiplier(2)

triple = make_multiplier(3)

print('double(10):', double(10))

print('triple(10):', triple(10))

print('apply_operation squares:', apply_operation([1, 2, 3], lambda x: x * x))

print('decorated_add(4, 5):', decorated_add(4, 5))

print('lambda_examples:', lambda_examples())

if __name__ == '__main__':

run_demo()