Code Dojo (Hackerrank melodious passwords) solution

code.py

#!/bin/python3

import sys
import itertools
import functools

n = int(input().strip())

letters = [
    [x for x in "aeiou"],
    [x for x in "bcdfghjklmnpqrstvwxz"]
    ]

def memoize(f):
    memo = {}
    def helper(x,y):
        if (x,y) not in memo:            
            memo[(x,y)] = f(x,y)
        return memo[(x,y)]
    return helper

def pwords(n,start_w_cons):
    if n == 1:
        return letters[start_w_cons]
    prod = itertools.product(letters[start_w_cons], pwords(n-1, not start_w_cons))
    return prod

def unnest(tup):
    if(isinstance(tup, str)):
        return tup
    else:
        return tup[0] + unnest(tup[1])

pwords = memoize(pwords)

all_pwords = list(pwords(n,True)) + list(pwords(n,False))
for i in all_pwords:
    print(unnest(i))