如何有效统计Python中每个单词的出现次数

def count_words(text):
    # 去除标点符号和换行符
    text = text.replace(".", "").replace(",", "").replace("?", "").replace("!", "").replace("\n", "")
    # 将文本转换为小写
    text = text.lower()
    # 按空格分割文本为单词列表
    words = text.split(" ")
    # 创建一个空字典来存储单词和出现次数
    word_count = {}
    
    for word in words:
        if word in word_count:
            # 如果单词已经在字典中，增加其出现次数
            word_count[word] += 1
        else:
            # 如果单词不在字典中，将其添加到字典并设置出现次数为1
            word_count[word] = 1
    
    return word_count

# 测试代码
text = "This is a test. This is only a test."
result = count_words(text)
print(result)

{'this': 2, 'is': 2, 'a': 2, 'test': 2, 'only': 1}