Python Comprehensions and Generators for Beginners

# Demonstrates list comprehensions, dict comprehensions, set comprehensions, and generators

def demonstrate_comprehensions():
    # List comprehension: squares of even numbers
    numbers = range(1, 11)
    even_squares = [n ** 2 for n in numbers if n % 2 == 0]
    
    # Dict comprehension: number to its factorial
    factorial = {}
    result = 1
    for i in range(1, 6):
        result *= i
        factorial[i] = result
    dict_comp = {k: v for k, v in factorial.items() if k > 2}
    
    # Set comprehension: unique first letters
    words = ["apple", "banana", "avocado", "cherry"]
    first_letters = {w[0] for w in words}
    
    # Generator expression: sum of squares without storing intermediate list
    sum_squares = sum(x * x for x in range(1, 6))
    
    print(f"Even squares: {even_squares}")
    print(f"Dict comp (keys > 2): {dict_comp}")
    print(f"Unique first letters: {first_letters}")
    print(f"Sum of squares (generator): {sum_squares}")
    
    # Generator function example
    def fibonacci(limit):
        a, b = 0, 1
        while a < limit:
            yield a
            a, b = b, a + b
    
    fib_generator = fibonacci(100)
    print(f"Fibonacci < 100: {list(fib_generator)}")

if __name__ == "__main__":
    demonstrate_comprehensions()