🔧 Functions Part II

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# Functions in python

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# what is function?
A function is a block of code that performs a specific task.
it is reusable and helps to organize the code efficiently
1@ code reusability--write once and use multiple times
2@ modularity--Divide the code into smaller and manageable parts
3@ Reduces Redundancy--aviod writing the same code repatibilty
4@ Improved Readability--makes programs easier to understand

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Types of functions
1@ Built-in functions
2@ User-defined functions
3@ lambda(annoymous) functions

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#for any word when you add a parenthis is a function

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print("to print")

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# Built-in-functions
print()
max()
min()
sum()
len()

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flow=input("enter a name")
print(flow)

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import builtins
print(dir(builtins))

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list1=[23,34,56,78,89]
avg=sum(list1)/len(list1)
avg

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import statistics
list1=[23,34,56,78,89]
s=statistics.mean(list1)
s

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max(list1)

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min(list1)

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#user-defined function is created by the user to perform a specific task.

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# syntax
def hello():  # defining a function
  # function block of code
hello()   # calling function

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# simple function without parameters
def greet():
  print("hello welcome to fuctions in python")

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greet()

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greet1()

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# syntax
def hello(parameters):  # defining a function
  # function block of code
hello(arguments)   # calling function

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greet("vishal")

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greet("aravind")

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Function arguments in python
1@ positional arguments
2@ default arguments/keyword arguments
3@ arbitary Keyword arguments
4@ arbitary non keyword arguments

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# positional argument
def greet(name):
  print(f"hello {name}")

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greet(3567)

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greet("azar")

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greet("rahul","aravind")

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# positional argument
def intro(name,age):
  print(f"hello my name is {name} , and  my age is {age}")

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intro(65,"banu",67)

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intro("banu")

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# default arguments/keyword arguments

def greet(name="rahul"):
  print(f"hello,{name}!")

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greet() # no argument are passed

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greet("alice") # positional argument is passed

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# positional arguments
def student(marks,name,age=21):
  print(f"name:{name} with age:{age} and marks:{marks}")

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student(33,"tarun",55)

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student("rahul",23) # Positional arguments

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student(90,"rahul",34) # wrong order of arguments

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student(marks=90,name="taarun",age=23) # keyword arguments without order

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student(44,name="aravind") # positional and keyword arguments

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student(name="aravind",44) # positional and keyword arguments

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student(marks=90,"rahul",23) # positional and keyword arguments

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# positional arguments
def student(marks,name,age=21):
  print(f"name:{name} with age:{age} and marks:{marks}")

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student(name="rahul",marks=90) # positional and keyword arguments

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a=9
print(a)

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# keyword arguments
def employee(name,salary,department="IT"):
  print(f"name:{name} with salary:{salary} and department:{department}")

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employee("rahul",23000,"HR")

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#In Python, return is used inside a function to send a value back to the caller and end the function immediately.

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

result=add(3,4)  # store the returned value
print(result)

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# function with return
def jack(a,b):
   add=a+b
   sub=a-b
   return(sub)
   return(add)
jack(5,4)

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# function with return
def jack(a,b):
   add=a+b
   sub=a-b
   return (sub,add)
result=jack(5,4)
print(result)

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# function with return
def jack(a,b):
   add=a+b
   sub=a-b
   return(sub)    # you cannot use a loop inside the function with mul return values
   return(add)
jack(5,4)

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def introduce(name="Sandip", age=0, marks=0):
  print(f"My name is {name}! and I am {age} years old. My marks are {marks}.")
introduce(marks = 100, age=30)

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def jack(a,b):
  sub = a - b
  sum = a + b
  return(sub, sum)
jack(3,3)

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# simple calculator
def add(a, b):
    return a + b

def subtract(a, b):
    return a - b

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

def divide(a, b):
    if b == 0:
        return "Error: Cannot divide by zero!"
    return a / b

# Real-time execution
print("---- Calculator ----")
a = float(input("Enter first number: "))
b = float(input("Enter second number: "))

choice = input("Choose operation (+, -, *, /): ")

if choice == '+':
    print("Result:", add(a, b))
elif choice == '-':
    print("Result:", subtract(a, b))
elif choice == '*':
    print("Result:", multiply(a, b))
elif choice == '/':
    print("Result:", divide(a, b))
else:
    print("Invalid choice!")

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balance = 1000 # global function

def deposit(amount):
    global balance
    balance += amount
    return balance

def withdraw(amount):
    global balance
    if amount > balance:
        return "Insufficient balance!"
    balance -= amount
    return balance

print("---- ATM ----")
while True:
    print("\n1. Deposit\n2. Withdraw\n3. Check Balance\n4. Exit")
    choice = input("Enter choice: ")

    if choice == '1':
        amt = float(input("Enter amount to deposit: "))
        print("New Balance:", deposit(amt))

    elif choice == '2':
        amt = float(input("Enter amount to withdraw: "))
        print("New Balance:", withdraw(amt))

    elif choice == '3':
        print("Balance:", balance)

    elif choice == '4':
        print("Thank you! Visit again.")
        break
    else:
        print("Invalid choice!")

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# arbitary arguments
1@ *args(non-keyword arbitary arguments)
2@ **kwargs(keyword arbitary arguments)
are called as arbitary arguments/special arguments that allows functions
to accept a variable number of arguments.

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# *args---accepts any number of positional arguments
# it allows to pass multiple arguments into a function
# These arguments are packed into a tuple inside the function

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# using *args
def add_numbers(*david):
  return sum(david)   # args is a tuple

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add_numbers(2,3,4,5,6,5,4,3)

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result=[3,4,5,6,7,8,9]
total = add_numbers(*result)
print(total)

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#iterating over *args
def print_names(*names):
  for name in names:
    print(f"Hello,{name}!")

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print_names("rahul","Tarun","sachin","Dinesh","ritesh")

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# Mixing regular arguments with *args

def greet(Title,name="aravind Reddy",*names):
  for name in names:
    print(f"{Title}{name}")

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greet("Dr.","Rahul","Tarun","sachin","Dinesh")

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dicti={"name":"rahul","age":23,"marks":90}

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dicti.values()

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#**kwargs---allows passing multiple keyword arguments to a function.
# These arguments are stored in a dictionary inside the function

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# using **kwargs
def print_details(**kwargs):
  for key,value in kwargs.items():
    print(f"{key}:>>>>>{value}")

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print_details(name="rahul",age=23,marks=90,grade="A",loaction="bangalore",class1="first",batch="nov")

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# mixing regular arguments with **kwargs
def display_students(name="alice",**details):
  print(f"student:{name}")
  for key,value in details.items():
    print(f"{key}:{value}")

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display_students(age=23,grade="A",city="bangalore")

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def place_order(item, quantity=1, *toppings, **customer):
    # Base prices
    menu = {
        "pizza": 200,
        "burger": 120,
        "pasta": 180
    }

    # Topping prices
    topping_prices = {
        "cheese": 30,
        "olives": 20,
        "mushrooms": 25
    }

    item = item.lower()

    if item not in menu:
        print("Item not available!")
        return

    print("\n--- ORDER SUMMARY ---")
    print(f"Item: {item.title()}")
    print(f"Quantity: {quantity}")

    # Step 1: Base price
    base_price = menu[item]
    print(f"Base Price (each): ₹{base_price}")

    # Step 2: Topping cost calculation (clear breakdown)
    topping_cost = 0
    if toppings:
        print("\nToppings Added:")
        for t in toppings:
            cost = topping_prices.get(t.lower(), 0)
            print(f"  {t} : ₹{cost}")
            topping_cost += cost
    else:
        print("\nNo toppings added.")

    print(f"\nTotal Topping Cost (per item): ₹{topping_cost}")

    # Step 3: Final calculation
    print("\n--- BILL CALCULATION ---")
    print(f"Base Price     : ₹{base_price}")
    print(f"Toppings       : ₹{topping_cost}")
    per_item_total = base_price + topping_cost
    print(f"Total per item : ₹{per_item_total}")

    final_bill = per_item_total * quantity
    print(f"Quantity ({quantity}) × ₹{per_item_total} = ₹{final_bill}")

    # Customer info (**kwargs)
    if customer:
        print("\n--- CUSTOMER DETAILS ---")
        for key, value in customer.items():
            print(f"{key.capitalize()}: {value}")

    print("\nFinal Amount to Pay: ₹", final_bill)
    print("--------------------------\n")

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#Basic Order
place_order("Pizza")

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#With toppings
place_order("Burger", 2, "Cheese", "Olives")

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# Full order with customer info
place_order(
    "Pasta", 1, "olives","Mushrooms",
    name="Alice",
    address="123 Main Street",
    phone="9876543210"
)

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# lambda function---anonymous function(one-line function)
#syntax---lambda arguments:expression
# only one expression is allowed

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add_all=lambda x,y,z,d:x-y+z+d
add_all(3,5,4,4)

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square=lambda x:x**2
square(23)

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square(23,45,88)

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numbers=[3,4,6,6,7]
square_map=tuple(map(lambda x:x**2,numbers))
print(square_map)