将 for 语句转换为列表理解时出现问题

Question

我想将下面的代码转换为列表理解形式：

word_list = ["cat","dog","rabbit"]
letter_list = []
for a_word in word_list:
   for a_letter in a_word:
      if a_letter not in letter_list:
        letter_list.append(a_letter)
print(letter_list)

我已经做到了：

word_list = ["cat" , "dog" , "rabbit"]
letter_list = []
letter_list = [a_letter for a_word in word_list for a_letter in a_word if a_letter not in letter_list]
print(letter_list)

但输出显示了我不想要的重复项。我该怎么办？

Answer 1

您的问题通过一套更好地解决：

word_list = ["cat","dog","rabbit"]
letter_set = {letter for word in word_list for letter in word}