Python Programming Solutions

# Simple Hello World program
print("Hello, World!")

# Python program structure example

# Import statements
import math

# Global variable
PI = 3.14159

# Function definition
def calculate_area(radius):
    """Calculate area of a circle."""
    return PI * radius ** 2

# Main program
if __name__ == "__main__":
    # Variable declaration
    radius = 5
    
    # Function call and output
    area = calculate_area(radius)
    print(f"Area of circle with radius {radius} is: {area:.2f}")
    
    # Using imported module
    print(f"Square root of 16 is: {math.sqrt(16)}")

# Python data types examples

# Numeric types
age = 25                    # Integer
price = 19.99              # Float
complex_num = 3 + 4j       # Complex number

# Sequence types
name = "Alice"             # String
numbers_list = [1, 2, 3]   # List
numbers_tuple = (1, 2, 3)  # Tuple

# Mapping type
person = {"name": "Alice", "age": 25}  # Dictionary

# Set types
unique_numbers = {1, 2, 3, 3}  # Set (duplicates removed)

# Boolean type
is_valid = True             # Boolean

# None type
result = None               # NoneType

# Output values and types
print("Type of age:", type(age))
print("Type of price:", type(price))
print("Type of name:", type(name))
print("Type of numbers_list:", type(numbers_list))
print("Type of person:", type(person))
print("Type of is_valid:", type(is_valid))
print("Type of result:", type(result))

# Set automatically removes duplicates
print("Unique numbers set:", unique_numbers)

# Constants and literals in Python

# Convention: Use uppercase for constants
PI = 3.14159
MAX_SIZE = 100

# Literals examples
decimal = 100              # Decimal literal
binary = 0b1100100        # Binary literal (100 in decimal)
octal = 0o144             # Octal literal (100 in decimal)
hexadecimal = 0x64        # Hexadecimal literal (100 in decimal)

# Float literals
float1 = 3.14
float2 = 3.14e-2          # Scientific notation (0.0314)

# String literals
single_quoted = 'Hello'
double_quoted = "World"
triple_quoted = '''Multi-line
string'''

# Boolean literals
true_value = True
false_value = False

# Collection literals
list_literal = [1, 2, 3]
tuple_literal = (1, 2, 3)
dict_literal = {"key": "value"}
set_literal = {1, 2, 3}

print("PI:", PI)
print("MAX_SIZE:", MAX_SIZE)
print("Binary 0b1100100:", binary)
print("Hexadecimal 0x64:", hexadecimal)
print("Scientific notation 3.14e-2:", float2)
print("Multi-line string:", triple_quoted)

# Basic input and output operations in Python

# Getting input from user
name = input("Enter your name: ")
age = int(input("Enter your age: "))
height = float(input("Enter your height (in meters): "))

# Displaying output
print("\n--- User Information ---")
print("Name:", name)
print("Age:", age)
print("Height:", height, "meters")

# Formatted output
print(f"\nFormatted: {name} is {age} years old and {height:.2f}m tall")

# Multiple values output
print("Name:", name, "Age:", age, "Height:", height)

# Output with separator
print(name, age, height, sep=" | ")

# Output to file
with open("output.txt", "w") as file:
    file.write(f"Name: {name}\nAge: {age}\nHeight: {height}\n")

print("\nData also written to output.txt file")

# Operators in Python

a = 10
b = 3

# Arithmetic operators
print("a + b =", a + b)
print("a - b =", a - b)
print("a * b =", a * b)
print("a / b =", a / b)      # True division
print("a // b =", a // b)    # Floor division
print("a % b =", a % b)      # Modulus
print("a ** b =", a ** b)    # Exponentiation

# Assignment operators
c = a
c += b
print("c += b:", c)
c -= b
print("c -= b:", c)

# Comparison operators
print("a == b:", a == b)
print("a != b:", a != b)
print("a > b:", a > b)
print("a <= b:", a <= b)

# Logical operators
x = True
y = False
print("x and y:", x and y)
print("x or y:", x or y)
print("not x:", not x)

# Identity operators
list1 = [1, 2, 3]
list2 = [1, 2, 3]
list3 = list1
print("list1 is list2:", list1 is list2)  # False (different objects)
print("list1 is list3:", list1 is list3)  # True (same object)
print("list1 == list2:", list1 == list2)  # True (same content)

# Membership operators
numbers = [1, 2, 3, 4, 5]
print("3 in numbers:", 3 in numbers)
print("6 not in numbers:", 6 not in numbers)

# Bitwise operators
print("a & b (bitwise AND):", a & b)
print("a | b (bitwise OR):", a | b)
print("a ^ b (bitwise XOR):", a ^ b)
print("~a (bitwise NOT):", ~a)
print("a << 1 (left shift):", a << 1)
print("a >> 1 (right shift):", a >> 1)

# If-else statements in Python

number = int(input("Enter a number: "))

# Simple if statement
if number > 0:
    print("The number is positive.")

# If-else statement
if number % 2 == 0:
    print("The number is even.")
else:
    print("The number is odd.")

# If-elif-else ladder
if number > 0:
    print("Positive number")
elif number < 0:
    print("Negative number")
else:
    print("Zero")

# Nested if statements
if number >= 0:
    if number == 0:
        print("Zero")
    else:
        print("Positive number")
else:
    print("Negative number")

# Conditional expressions (ternary operator)
result = "Even" if number % 2 == 0 else "Odd"
print(f"The number is {result}")

# Multiple conditions
if number > 0 and number % 2 == 0:
    print("Positive even number")
elif number > 0 and number % 2 != 0:
    print("Positive odd number")
elif number < 0:
    print("Negative number")
else:
    print("Zero")

# Match case statement (Python 3.10+)

def process_grade(grade):
    """Process grade using match case."""
    grade = grade.upper()
    
    match grade:
        case "A":
            return "Excellent!"
        case "B":
            return "Well done!"
        case "C":
            return "Good job!"
        case "D":
            return "You passed, but could do better."
        case "F":
            return "Sorry, you failed."
        case _:
            return "Invalid grade entered."

# Get input from user
grade = input("Enter your grade (A, B, C, D, F): ")
result = process_grade(grade)
print(result)

# More complex pattern matching
def describe_value(value):
    """Describe value using pattern matching."""
    match value:
        case 0:
            return "Zero"
        case 1 | 2 | 3:
            return "Small number"
        case n if n > 3 and n < 10:
            return "Medium number"
        case n if n >= 10:
            return "Large number"
        case _:
            return "Not a number or negative"

# Test the function
print(describe_value(0))     # Zero
print(describe_value(2))     # Small number
print(describe_value(5))     # Medium number
print(describe_value(15))    # Large number

# Pattern matching with lists
def process_list(lst):
    """Process list using pattern matching."""
    match lst:
        case []:
            return "Empty list"
        case [x]:
            return f"Single element: {x}"
        case [x, y]:
            return f"Two elements: {x} and {y}"
        case [x, y, *rest]:
            return f"First two: {x}, {y}, rest: {rest}"
        case _:
            return "Not a list"

print(process_list([]))              # Empty list
print(process_list([1]))             # Single element: 1
print(process_list([1, 2]))          # Two elements: 1 and 2
print(process_list([1, 2, 3, 4]))    # First two: 1, 2, rest: [3, 4]

# For loops in Python

# Basic for loop with range
print("Counting from 1 to 5:")
for i in range(1, 6):
    print(i, end=" ")
print("\n")

# For loop with list
fruits = ["apple", "banana", "cherry"]
print("Fruits:")
for fruit in fruits:
    print(fruit, end=" ")
print("\n")

# For loop with index and value
print("Fruits with index:")
for index, fruit in enumerate(fruits):
    print(f"{index}: {fruit}")

# Nested for loop (multiplication table)
print("\nMultiplication Table (1-5):")
for i in range(1, 6):
    for j in range(1, 6):
        print(i * j, end="\t")
    print()

# For loop with dictionary
person = {"name": "Alice", "age": 25, "city": "New York"}
print("\nPerson details:")
for key, value in person.items():
    print(f"{key}: {value}")

# For loop with string
message = "Python"
print("\nCharacters in 'Python':")
for char in message:
    print(char, end=" ")
print()

# For loop with else clause
print("\nSearching for number 6:")
numbers = [1, 2, 3, 4, 5]
for num in numbers:
    if num == 6:
        print("Number 6 found!")
        break
else:
    print("Number 6 not found in the list.")

# Using zip to iterate over multiple sequences
names = ["Alice", "Bob", "Charlie"]
ages = [25, 30, 35]
print("\nPeople and their ages:")
for name, age in zip(names, ages):
    print(f"{name} is {age} years old")

# While loops in Python

# While loop example
print("While loop - counting from 1 to 5:")
i = 1
while i <= 5:
    print(i, end=" ")
    i += 1
print("\n")

# Python doesn't have a built-in do-while loop, but we can simulate it
print("Simulated do-while loop - counting from 1 to 5:")
j = 1
while True:
    print(j, end=" ")
    j += 1
    if j > 5:
        break
print("\n")

# Practical example: Sum of numbers until 0 is entered
total = 0
print("Enter numbers to sum (enter 0 to stop):")

while True:
    try:
        number = float(input("Enter a number: "))
        if number == 0:
            break
        total += number
    except ValueError:
        print("Please enter a valid number!")

print(f"Sum of entered numbers: {total}")

# While loop with else clause
print("\nSearching for number 6:")
numbers = [1, 2, 3, 4, 5]
index = 0
while index < len(numbers):
    if numbers[index] == 6:
        print("Number 6 found!")
        break
    index += 1
else:
    print("Number 6 not found in the list.")

# Using while loop for input validation
while True:
    age_input = input("\nPlease enter your age (positive number): ")
    if age_input.isdigit() and int(age_input) > 0:
        age = int(age_input)
        print(f"Your age is: {age}")
        break
    else:
        print("Invalid input. Please enter a positive number.")

# While loop with condition
print("\nCountdown from 5:")
count = 5
while count > 0:
    print(count, end=" ")
    count -= 1
print("Blastoff!")

# Lists and list operations in Python

# Creating lists
numbers = [1, 2, 3, 4, 5]
fruits = ["apple", "banana", "cherry"]
mixed = [1, "hello", 3.14, True]

# Accessing elements
print("First fruit:", fruits[0])
print("Last number:", numbers[-1])

# Slicing
print("First three numbers:", numbers[:3])
print("Last two fruits:", fruits[-2:])

# List operations
numbers.append(6)          # Add element
numbers.insert(2, 99)      # Insert at position
numbers.remove(99)         # Remove element
popped = numbers.pop()     # Remove and return last element
print("After operations:", numbers)

# List comprehension
squares = [x**2 for x in range(1, 6)]
print("Squares:", squares)

# Sorting
numbers.sort()
print("Sorted:", numbers)
numbers.sort(reverse=True)
print("Reverse sorted:", numbers)

# Tuples and dictionaries in Python

# Tuples (immutable)
coordinates = (10, 20)
print("Coordinates:", coordinates)
print("X coordinate:", coordinates[0])

# Dictionary (key-value pairs)
person = {
    "name": "Alice",
    "age": 25,
    "city": "New York"
}

# Accessing values
print("Name:", person["name"])
print("Age:", person.get("age"))

# Adding/updating
person["email"] = "alice@example.com"
person["age"] = 26

# Dictionary methods
print("Keys:", person.keys())
print("Values:", person.values())
print("Items:", person.items())

# Dictionary comprehension
squares = {x: x**2 for x in range(1, 6)}
print("Squares dictionary:", squares)