如何提取某个单词前面的另一个单词？

def extract_previous_word(text, target_word):
    words = text.split()  # 分割文本为单词列表
    for i in range(1, len(words)):
        if words[i] == target_word:
            return words[i-1]  # 返回目标单词前面的单词
    return None  # 如果未找到目标单词，则返回None

# 示例用法
text = "This is an example sentence."
target_word = "example"
previous_word = extract_previous_word(text, target_word)
print(previous_word)  # 输出: "an"