您使用的是列表而不是字典来存储词频。您不能像这样使用列表来存储键-值对，而需要使用字典来代替。下面是如何修改代码以使用字典来存储词频：

file = open(fname,'r')
word_frequencies = {} # use a dictionary to store the word frequencies

for line in file:
    line = line.lower()
    words = line.split(' ')
    for word in words:
        if word in word_frequencies:
            word_frequencies[word] += 1
        else:
            word_frequencies[word] = 1

然后迭代关键点并找到最小和最大频率

# iterate over the keys and values in the word_frequencies dictionary
# and find the word with the max and min frequency
max_word = None
min_word = None
max_frequency = 0
min_frequency = float('inf')

for word, frequency in word_frequencies.items():
    if frequency > max_frequency:
        max_word = word
        max_frequency = frequency
    if frequency < min_frequency:
        min_word = word
        min_frequency = frequency

打印结果

print("Max frequency:", max_word, max_frequency)
print("Min frequency:", min_word, min_frequency)