使用 Python 3：def show_flashcard():        """ Show the user a random key and ask them        to define it. Show the definition        when the user presses return. it then asks if user        knew definition or not if they do delets the word and        then asks if they want to continue or quit.    """    random_key = choice(list(glossary))    print('Define: ', random_key)    input('Press return to see the definition')    print(glossary[random_key])    import time    time.sleep(1) # delay for 1 seconds    print('Did you know the answer')    user_input = input('y or n: ')    if user_input == 'n':        print( 'Do not give  up you can only learn by practice')        time.sleep(1) # delay for 1 seconds        user_input = input('Enter s to show a flashcard and q to quit: ')    if user_input == 'y':        print( 'Congratulations , the word wil now be removed from the dictionary')    del (glossary[random_key])# Set up the glossaryglossary = {'1: word1':'definition1',            '2: word2':'definition2',            '3: word3':'definition3'}# The interactive loopexit = Falsewhile not exit:    if glossary == {''}:        exit = True       user_input = input('Enter s to show a flashcard and q to quit: ')    if user_input == 'q':        exit = True    elif user_input == 's':        show_flashcard()    else:        print('You need to enter either q or s.')當詞匯表為空時，我似乎無法讓這個循環自動退出。我已經嘗試了很多東西，從if glossary = 0 then exit is true，但我似乎無法到達任何地方。它讓我發瘋。