Guess the Word

import random
a = input("Choose a difficulty \n \
Easy-10 Lives \n \
Medium-7 Lives \n \
Hard-5 Lives \n \
Choose a difficulty: ")
a = a.lower()
if a in {"easy", "medium", "hard"}:
    print("Difficulty Selected")
else:
    print("Invalid Input!")
if a == 'easy':
    print("You have 10 lives left.")
    lives = 10
if a == 'medium':
    print("You have 7 lives left.")
    lives = 7
if a == 'hard':
    print("You have 5 lives left.")
    lives = 5
words = ['fairy', 'birds', 'doggy', 'frogs', 'phone', 'green', 'hello', ] #Dont put your nose where it doesnt belong
secretword = random.choice(words)
clue = list('?????')
heart = u'\u2764'
guess_correctly = False

def update_clue(guessed_letter, secretword, clue):
    index = 0
    while index < len(secretword):
        if guessed_letter == secretword[index]:
            clue[index] = guessed_letter
        index = index + 1

while lives > 0:
    print(clue)
    print('Lives Left: ' + heart * lives)
    guess = input('Guess a letter of the entire phrase!: ')

    if guess == secretword:
        guess_correctly = True
        break

    if guess in secretword:
        update_clue(guess, secretword, clue)
    else:
        print('Incorrect! You lost a life!')
        lives = lives - 1

if guess_correctly == True:
    print('You Won!  The secret word was ' + secretword)
else:
    print('You lost! The secret word was ' + secretword)