识别字符串中最常用的单词

def find_most_common_word(string):
    # 将字符串转换为小写，并去除标点符号
    string = string.lower()
    string = ''.join(c for c in string if c.isalnum() or c.isspace())

    # 分割字符串为单词列表
    words = string.split()

    # 统计每个单词的出现次数
    word_count = {}
    for word in words:
        if word in word_count:
            word_count[word] += 1
        else:
            word_count[word] = 1

    # 找到出现次数最多的单词
    most_common_word = ''
    max_count = 0
    for word, count in word_count.items():
        if count > max_count:
            most_common_word = word
            max_count = count

    return most_common_word

# 测试
string = "This is a test string. This string is used for testing purposes."
result = find_most_common_word(string)
print("最常用的单词是:", result)