Console Word game in Python: OOP Approach

word_game.py

import random as r


class WordGame:
    word_list = ['programmer', 'python', 'defenestrate']
    secret_word = r.choice(word_list).upper()
    guessed_letters = []

    def __init__(self, guesses=9, letters='ABCDEFGHIJKLMNOPQRSTUVWXYZ'):
        self.guesses = guesses
        self.letters = list(letters)

    def __format_word(self):
        formatted_string = ''
        for letter in self.secret_word:
            if letter in self.guessed_letters:
                formatted_string += letter
            else:
                formatted_string += '-'
        return formatted_string

    def __display_info(self):
        letters = self.letters
        available_letters = ' '.join([
            letter for letter in letters if letter not in self.guessed_letters
        ])
        print(self.__format_word())
        print(f'Guesses left: {self.guesses}.')
        print(f'Available letters: {available_letters}.')

    def __check_guess(self, guess):
        letters, guessed = self.letters, self.guessed_letters
        if guess in letters and len(guess) == 1 and guess not in guessed:
            self.guessed_letters.append(guess)
            if guess in self.secret_word:
                print('Good guess!')
            else:
                print('Bad guess!')
                self.guesses -= 1
        else:
            if len(guess) != 1:
                print('You must enter one letter, no more, no less!')
            elif guess.upper() not in letters:
                print('Your guess has to be a letter!')
            elif guess in self.guessed_letters:
                print('This letter has been tried already!')
        self.__display_info()

    def __can_be_formed_from(self):
        for letter in self.secret_word:
            if letter not in self.guessed_letters:
                return False
        return True

    def start(self):
        word_length = len(self.secret_word)
        print(f'You have chosen a/an {word_length}-letter word.')
        while self.guesses > 0:
            guess = input('Enter a letter: ')
            guess = guess.upper()
            self.__check_guess(guess)
            if self.__can_be_formed_from():
                return print('YOU WON!')
        print('YOU LOST! You ran out of guesses.')
        print(f'The word was {self.secret_word}')


if __name__ == '__main__':
    new_game = WordGame()
    new_game.start()