Python - 我的频率函数效率低下

Question

我正在编写一个函数，它返回单词列表中出现次数最多的单词出现的次数。

def max_frequency(words):
    """Returns the number of times appeared of the word that
    appeared the most in a list of words."""

    words_set = set(words)
    words_list = words
    word_dict = {}

    for i in words_set:
        count = []
        for j in words_list:
            if i == j:
                count.append(1)
        word_dict[i] = len(count)

    result_num = 0
    for _, value in word_dict.items():
        if value > result_num:
            result_num = value
    return result_num

例如:

words = ["Happy", "Happy", "Happy", "Duck", "Duck"]
answer = max_frequency(words)
print(answer)

3

但是当处理列表中的大量单词时，此函数会很慢，例如，250,000 个单词的列表此函数需要超过 4 分钟才能呈现输出。所以我正在寻求帮助来调整这个。

我不想导入任何东西。

Answer 1

为了防止对每个唯一单词多次遍历列表，您只需迭代一次并更新每个计数的字典值即可。

counts = {}
for word in words:
    counts[word] = counts.get(word, 0) + 1

输出:

>>> print(max(counts.values()))
3

<小时/>

话虽如此，使用 defaultdict 而不是 get 或使用 collections.Counter 可以做得更好。 ...如果你有选择的话，限制自己在 Python 中不导入从来都不是一个好主意。

例如，使用collections.Counter:

from collections import Counter
counter = Counter(words)
most_common = counter.most_common(1)