Write a Python module that solves a problem.

Answer 1

Sure! Let’s create a Python module that solves a common problem: calculating the nth Fibonacci number. The Fibonacci sequence is a series of numbers where each number is the sum of the two preceding ones, usually starting with 0 and 1.

The nth Fibonacci number can be calculated using a few different methods, but for simplicity, we will implement an iterative approach as well as a recursive approach.

Fibonacci Module

Here's how the Python module could look:

# fibonacci.py

def fibonacci_iterative(n):
    """
    Calculate the nth Fibonacci number using an iterative approach.

    Args:
        n (int): The index of the Fibonacci sequence.

    Returns:
        int: The nth Fibonacci number.
    
    Raises:
        ValueError: If n is less than 0.
    """
    if n < 0:
        raise ValueError("n must be a non-negative integer.")
    elif n == 0:
        return 0
    elif n == 1:
        return 1
    
    a, b = 0, 1
    for _ in range(2, n + 1):
        a, b = b, a + b
    return b

def fibonacci_recursive(n):
    """
    Calculate the nth Fibonacci number using a recursive approach.

    Args:
        n (int): The index of the Fibonacci sequence.

    Returns:
        int: The nth Fibonacci number.
    
    Raises:
        ValueError: If n is less than 0.
    """
    if n < 0:
        raise ValueError("n must be a non-negative integer.")
    elif n == 0:
        return 0
    elif n == 1:
        return 1
    
    return fibonacci_recursive(n - 1) + fibonacci_recursive(n - 2)

if __name__ == "__main__":
    import sys
    
    if len(sys.argv) != 3:
        print("Usage: python fibonacci.py <method: iterative|recursive> <n>")
        sys.exit(1)

    method = sys.argv[1].lower()
    n = int(sys.argv[2])

    if method == "iterative":
        result = fibonacci_iterative(n)
    elif method == "recursive":
        result = fibonacci_recursive(n)
    else:
        print("Unknown method. Choose either 'iterative' or 'recursive'.")
        sys.exit(1)

    print(f"The {n}th Fibonacci number is: {result}")

How to use the module

1. Save the code above into a file named fibonacci.py.
2. Open a terminal or command prompt.
3. Navigate to the directory where fibonacci.py is located.
4. Execute the script using one of the following commands:

For the iterative approach:

python fibonacci.py iterative 10

For the recursive approach:

python fibonacci.py recursive 10

Replace 10 with any non-negative integer n to calculate the nth Fibonacci number.

Explanation

• The module defines two functions: fibonacci_iterative and fibonacci_recursive which calculate the nth Fibonacci number using iterative and recursive methods, respectively.
• It checks that the input is valid (non-negative integer) and raises a ValueError for invalid inputs.
• When the module is run directly, it accepts command-line arguments to specify the method and the desired Fibonacci number index.

Feel free to modify or expand upon this module as needed!