Unit II: Program Flow Control

# Basic condition evaluation
print(5 > 3)    # True
print(5 < 3)    # False
print(5 == 5)   # True
print(5 != 5)   # False

# Conditions with variables
age = 18
print(age >= 18)  # True

# Combining conditions
score = 85
print(score >= 60 and score <= 100)  # True

# Simple if statement
age = 20

if age >= 18:
    print("You are an adult")
    print("You can vote!")

# The above prints only if age >= 18

temperature = 35

if temperature > 30:
    print("It's a hot day!")
    print("Stay hydrated!")

# if-else statement
age = 16

if age >= 18:
    print("You are an adult")
else:
    print("You are a minor")

# Another example
number = 7

if number % 2 == 0:
    print(f"{number} is even")
else:
    print(f"{number} is odd")

# if-elif-else for multiple conditions
score = 85

if score >= 90:
    grade = 'A'
elif score >= 80:
    grade = 'B'
elif score >= 70:
    grade = 'C'
elif score >= 60:
    grade = 'D'
else:
    grade = 'F'

print(f"Your grade is: {grade}")

# Another example: Day of the week
day = 3

if day == 1:
    print("Monday")
elif day == 2:
    print("Tuesday")
elif day == 3:
    print("Wednesday")
elif day == 4:
    print("Thursday")
elif day == 5:
    print("Friday")
elif day == 6:
    print("Saturday")
elif day == 7:
    print("Sunday")
else:
    print("Invalid day")

# Nested if statements
age = 25
has_license = True

if age >= 18:
    print("Age requirement met")
    if has_license:
        print("You can drive!")
    else:
        print("You need a license to drive")
else:
    print("You are too young to drive")

# Login system example
username = "admin"
password = "secret123"

input_user = "admin"
input_pass = "secret123"

if input_user == username:
    if input_pass == password:
        print("Login successful!")
    else:
        print("Incorrect password")
else:
    print("User not found")

# Ternary operator: value_if_true if condition else value_if_false

age = 20
status = "adult" if age >= 18 else "minor"
print(status)  # adult

# One-liner for min/max
a, b = 10, 20
smaller = a if a < b else b
print(f"Smaller: {smaller}")  # 10

# With function calls
def check_even(n):
    return "Even" if n % 2 == 0 else "Odd"

print(check_even(7))   # Odd
print(check_even(10))  # Even

# Iterating over a list
fruits = ["apple", "banana", "cherry"]

for fruit in fruits:
    print(fruit)

# Output:
# apple
# banana
# cherry

# Iterating over a string
for char in "Python":
    print(char)

# Output: P y t h o n (each on new line)

# Processing list items
numbers = [1, 2, 3, 4, 5]

# Calculate sum
total = 0
for num in numbers:
    total += num
print(f"Sum: {total}")  # Sum: 15

# Create a new list with doubled values
doubled = []
for num in numbers:
    doubled.append(num * 2)
print(doubled)  # [2, 4, 6, 8, 10]

# Using enumerate() to get index
colors = ["red", "green", "blue"]
for index, color in enumerate(colors):
    print(f"{index}: {color}")

# Output:
# 0: red
# 1: green
# 2: blue

# Count vowels in a string
text = "Hello World"
vowels = "aeiouAEIOU"
count = 0

for char in text:
    if char in vowels:
        count += 1

print(f"Vowels count: {count}")  # Vowels count: 3

# Reverse a string
original = "Python"
reversed_str = ""

for char in original:
    reversed_str = char + reversed_str

print(reversed_str)  # nohtyP

# Check for palindrome
word = "radar"
is_palindrome = True

for i in range(len(word) // 2):
    if word[i] != word[-(i+1)]:
        is_palindrome = False
        break

print(f"'{word}' is palindrome: {is_palindrome}")  # True

# Iterating over dictionaries
student = {
    "name": "Alice",
    "age": 20,
    "grade": "A"
}

# Iterate over keys (default)
print("Keys:")
for key in student:
    print(key)

# Iterate over values
print("\nValues:")
for value in student.values():
    print(value)

# Iterate over key-value pairs
print("\nKey-Value pairs:")
for key, value in student.items():
    print(f"{key}: {value}")

# Output:
# Keys:
# name
# age
# grade
# 
# Values:
# Alice
# 20
# A
# 
# Key-Value pairs:
# name: Alice
# age: 20
# grade: A

# range(stop) - 0 to stop-1
print("range(5):")
for i in range(5):
    print(i, end=" ")  # 0 1 2 3 4
print()

# range(start, stop) - start to stop-1
print("\nrange(2, 7):")
for i in range(2, 7):
    print(i, end=" ")  # 2 3 4 5 6
print()

# range(start, stop, step)
print("\nrange(0, 10, 2):")
for i in range(0, 10, 2):
    print(i, end=" ")  # 0 2 4 6 8
print()

# Negative step (counting backwards)
print("\nrange(10, 0, -1):")
for i in range(10, 0, -1):
    print(i, end=" ")  # 10 9 8 7 6 5 4 3 2 1
print()

# Converting range to list
numbers = list(range(1, 6))
print(f"\nList from range: {numbers}")  # [1, 2, 3, 4, 5]

# Print multiplication table
n = 5
print(f"Multiplication table of {n}:")
for i in range(1, 11):
    print(f"{n} x {i} = {n * i}")

# Sum of first n natural numbers
n = 100
total = 0
for i in range(1, n + 1):
    total += i
print(f"\nSum of first {n} numbers: {total}")  # 5050

# Factorial calculation
num = 5
factorial = 1
for i in range(1, num + 1):
    factorial *= i
print(f"\n{num}! = {factorial}")  # 120

# Print a pattern
print("\nTriangle pattern:")
for i in range(1, 6):
    print("*" * i)
# *
# **
# ***
# ****
# *****

# Access list by index
fruits = ["apple", "banana", "cherry", "date"]
for i in range(len(fruits)):
    print(f"Index {i}: {fruits[i]}")

# Basic while loop
count = 1

while count <= 5:
    print(f"Count: {count}")
    count += 1  # Don't forget to increment!

print("Loop finished!")

# Output:
# Count: 1
# Count: 2
# Count: 3
# Count: 4
# Count: 5
# Loop finished!

# Sum until a condition
total = 0
num = 1

while total < 100:
    total += num
    num += 1

print(f"Sum reached {total} after adding numbers up to {num - 1}")

# Countdown
print("\nCountdown:")
seconds = 5
while seconds > 0:
    print(seconds)
    seconds -= 1
print("Blast off! 🚀")

# User input validation
password = ""
attempts = 3

while password != "secret" and attempts > 0:
    password = input(f"Enter password ({attempts} attempts left): ")
    attempts -= 1
    
    if password == "secret":
        print("Access granted!")
    elif attempts == 0:
        print("Too many attempts. Account locked!")
    else:
        print("Wrong password. Try again.")

# The else block runs when condition becomes False
# (but NOT when loop is broken with break)

count = 1

while count <= 3:
    print(f"Count: {count}")
    count += 1
else:
    print("Loop completed normally!")

# Output:
# Count: 1
# Count: 2
# Count: 3
# Loop completed normally!

# Searching example
numbers = [1, 3, 5, 7, 9]
target = 5
index = 0

while index < len(numbers):
    if numbers[index] == target:
        print(f"Found {target} at index {index}")
        break
    index += 1
else:
    print(f"{target} not found in list")

# break - exit loop immediately
print("Finding first even number:")
for num in [1, 3, 5, 4, 7, 8, 9]:
    if num % 2 == 0:
        print(f"Found even number: {num}")
        break
    print(f"Checking {num}...")

# Output:
# Checking 1...
# Checking 3...
# Checking 5...
# Found even number: 4

# Search in list
fruits = ["apple", "banana", "cherry", "date"]
search = "cherry"

for fruit in fruits:
    if fruit == search:
        print(f"Found '{search}'!")
        break
else:
    print(f"'{search}' not in list")

# continue - skip current iteration
print("Odd numbers from 1 to 10:")
for num in range(1, 11):
    if num % 2 == 0:
        continue  # Skip even numbers
    print(num, end=" ")

print()  # 1 3 5 7 9

# Skip specific items
fruits = ["apple", "banana", "cherry", "date"]
print("\nFruits (excluding banana):")
for fruit in fruits:
    if fruit == "banana":
        continue
    print(fruit)

# Process only valid data
data = [10, -5, 20, -3, 15, 0]
print("\nProcessing positive numbers:")
for value in data:
    if value <= 0:
        continue
    print(f"Processing: {value}")

# pass - placeholder that does nothing

# Empty loop (for later implementation)
for i in range(5):
    pass  # TODO: implement later

# Empty function
def future_function():
    pass  # Will implement later

# Empty class
class MyClass:
    pass

# Conditional placeholder
x = 10
if x > 5:
    pass  # Handle this case later
else:
    print("x is 5 or less")

# Ignoring specific cases
for num in range(1, 11):
    if num == 5:
        pass  # Intentionally do nothing for 5
    else:
        print(num, end=" ")  # 1 2 3 4 6 7 8 9 10

# else with for loop
print("Searching for 6 in [1, 2, 3, 4, 5]:")
for num in [1, 2, 3, 4, 5]:
    if num == 6:
        print("Found 6!")
        break
else:
    print("6 not found in list")

# else with for loop (found case)
print("\nSearching for 3 in [1, 2, 3, 4, 5]:")
for num in [1, 2, 3, 4, 5]:
    if num == 3:
        print("Found 3!")
        break
else:
    print("3 not found in list")

# Prime number checker
def is_prime(n):
    if n < 2:
        return False
    for i in range(2, int(n ** 0.5) + 1):
        if n % i == 0:
            return False
    else:
        return True

# Test prime numbers
for num in [2, 17, 18, 23, 25]:
    print(f"{num} is prime: {is_prime(num)}")

import random

# Number guessing game
secret = random.randint(1, 100)
attempts = 0
max_attempts = 7

print("🎮 Number Guessing Game!")
print("I'm thinking of a number between 1 and 100.")
print(f"You have {max_attempts} attempts.\n")

while attempts < max_attempts:
    guess = int(input("Enter your guess: "))
    attempts += 1
    
    if guess < secret:
        print("Too low! Try higher.")
    elif guess > secret:
        print("Too high! Try lower.")
    else:
        print(f"🎉 Congratulations! You got it in {attempts} attempts!")
        break
    
    remaining = max_attempts - attempts
    if remaining > 0:
        print(f"Attempts remaining: {remaining}\n")
else:
    print(f"\n😢 Game Over! The number was {secret}")

# Classic FizzBuzz problem
# Print numbers 1-100, but:
# - Print "Fizz" for multiples of 3
# - Print "Buzz" for multiples of 5
# - Print "FizzBuzz" for multiples of both

for num in range(1, 101):
    if num % 3 == 0 and num % 5 == 0:
        print("FizzBuzz")
    elif num % 3 == 0:
        print("Fizz")
    elif num % 5 == 0:
        print("Buzz")
    else:
        print(num)

# Print pyramid pattern
rows = 5

print("Pyramid Pattern:")
for i in range(1, rows + 1):
    # Print spaces
    for j in range(rows - i):
        print(" ", end="")
    # Print stars
    for k in range(2 * i - 1):
        print("*", end="")
    print()

# Output:
#     *
#    ***
#   *****
#  *******
# *********

# Inverted pyramid
print("\nInverted Pyramid:")
for i in range(rows, 0, -1):
    for j in range(rows - i):
        print(" ", end="")
    for k in range(2 * i - 1):
        print("*", end="")
    print()

# Find all prime numbers up to n
n = 50
primes = []

for num in range(2, n + 1):
    is_prime = True
    
    for i in range(2, int(num ** 0.5) + 1):
        if num % i == 0:
            is_prime = False
            break
    
    if is_prime:
        primes.append(num)

print(f"Prime numbers up to {n}:")
print(primes)

# Output: [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47]

# Simple calculator with loop
print("🧮 Simple Calculator")
print("Operations: +, -, *, /, ** (power)")
print("Type 'quit' to exit\n")

while True:
    expression = input("Enter expression (e.g., 5 + 3): ")
    
    if expression.lower() == 'quit':
        print("Goodbye!")
        break
    
    try:
        # Parse the expression
        parts = expression.split()
        num1 = float(parts[0])
        operator = parts[1]
        num2 = float(parts[2])
        
        # Perform calculation
        if operator == '+':
            result = num1 + num2
        elif operator == '-':
            result = num1 - num2
        elif operator == '*':
            result = num1 * num2
        elif operator == '/':
            if num2 == 0:
                print("Error: Division by zero!")
                continue
            result = num1 / num2
        elif operator == '**':
            result = num1 ** num2
        else:
            print("Invalid operator!")
            continue
        
        print(f"Result: {result}\n")
        
    except (ValueError, IndexError):
        print("Invalid input! Use format: number operator number\n")