Two examples of recursion: the fibonacci sequence, and the towers of hanoi.

recursion.py

#!/usr/bin/env python
"""
    Nii Mante
    November 23rd, 2016

    To execute the fibonacci sequence with 5 numbers, use a command like so

        python recursion.py fib -n 5

    To execute the hanoi game with 4 disks, use a command like so

        python recursion.py hanoi -d 4 
"""
import argparse 

def create_parser():
    parser = argparse.ArgumentParser(description="Execute examples of recursive programs") 
    subparsers = parser.add_subparsers(help="Sub help")
    
    # Fibonacci Parser
    fib_parser = subparsers.add_parser('fib')
    fib_parser.add_argument('-n', '--numbers', type=int, help="Amount of numbers to generate for fibonacci sequence", default=5)
    fib_parser.set_defaults(func=sequence)

    # Hanoi Parser
    hanoi_parser = subparsers.add_parser('hanoi')
    hanoi_parser.add_argument('-v', '--verbose', action="store_true", help="Set this flag to print each move out. Default behavior is to simply print the last tower")
    hanoi_parser.add_argument('-d', '--num_disks', type=int, help="Number of disks to start the Hanoi game with", default=3)
    hanoi_parser.set_defaults(func=hanoi)
    
    return parser

def sequence(args):

    def fibonacci(n):
        if n < 0:
            return 0
        if n == 0 or n == 1:
            return n

        return fibonacci(n - 1) + fibonacci(n - 2)

    n = args.numbers
    seq = []
    for i in range(n):
        seq.append(fibonacci(i))

    print seq

def hanoi(args):
    def move_disk(disk_num, from_tower, to_tower):
        print "moving disk: " + str(disk_num) + " from tower: " + str(from_tower) + " to tower: " + str(to_tower)

    def solve_hanoi(height, from_tower, to_tower, buffer_tower):
        if height > 0:
            solve_hanoi(height - 1, from_tower, buffer_tower, to_tower)
            move_disk(height, from_tower, to_tower)
            solve_hanoi(height - 1, buffer_tower, to_tower, from_tower)

    num_disks = args.num_disks
    solve_hanoi(num_disks, 0, 2, 1)

def main():
    args = create_parser().parse_args()
    args.func(args)
    """
    # Tower of hanoi
    solve_hanoi(3, 0, 2, 1)

    # Fibonacci
    print sequence(4)
    """

if __name__ == "__main__":
    main()