Getting an IF statement to recognize very specific characters

import random
import re

WORDS = ("python",
         "jumble",
         "easy",
         "difficult",
         "answer",
         "xylophone")

word = random.choice(WORDS)

word_length = len(word)

print("""
        Welcome to 'Random Word Guess'!
            Where randomly guessing
            words is the funnest!!!!

        Instructions:
        I will choose a random word from
        my memory banks.  I will then give
        you five guesses at letters in the
        word.  Then you have to guess the word
        after your letter guesses run out.
        You have five guesses!  Let's start!
""")

print("The length of the random word is",word_length,"characters.")

print("\nOK, begin your letter guesses!")

guessed_letters = ""
guess_tries = 0

while True:
    letter_guess = input("\nYour letter guess: ")
    if not re.match("^[a-z]*$",letter_guess):
        print("\nPlease use only the letters 'a' through 'z'!")
    if len(letter_guess) > 1:
        print("\nOnly one input character allowed!")
        continue
    if letter_guess not in word:
        print("\nNo")
        guess_tries += 1
    if letter_guess in word:
        print("\nYes")
        guessed_letters = guessed_letters + letter_guess
        guess_tries += 1
    elif guess_tries == 5:
        print("\nHere are the letters you've guessed:",guessed_letters)
        print("\nThat's the end of your guesses, now lets try to guess the word.")
        break

if letter_guess not in word:
        print("\nNo")
        guess_tries += 1

if letter_guess.isalpha() and letter_guess not in word:
        print("\nNo")
        guess_tries += 1