"""

07_functions.py

Purpose: defining functions, arguments, defaults, keyword args, *args, **kwargs, scope, lambda, documentation.

"""

def header(t): print("\n###", t, "###\n")

header("Defining & calling")

def add(a, b):

"""Return sum of a and b."""

return a + b

print("add(2,3):", add(2,3))

header("Default arguments and mutables gotcha")

def append_item(lst=None):

if lst is None:

lst = []

lst.append("item")

return lst

print("append_item:", append_item())

print("append_item again:", append_item()) # safe because we used None default

header("*args and **kwargs")

def demo(*args, **kwargs):

print("args:", args)

print("kwargs:", kwargs)

demo(1,2, x=3, y=4)

header("Scope: local vs global")

g = 10

def scope_demo():

g = 5 # local

print("local g:", g)

scope_demo()

print("global g:", g)

header("Lambda (anonymous) functions")

square = lambda x: x * x

print("square(5):", square(5))

header("Docstrings and type hints")

def greet(name: str) -> str:

"""Return greeting for name (type-hinted)."""

return f"Hello {name}"

print(greet("Khushal"))

header("Mini Exercises")

# 1) Write a function factorial(n) iterative and recursive versions.

# 2) Write a function that accepts *args and returns their average.