如何更改文本文件中每行的第一个单词？

def change_first_word(filename):
    with open(filename, 'r') as file:
        lines = file.readlines()

    modified_lines = []
    for line in lines:
        words = line.split()
        if len(words) > 0:
            words[0] = "new_word"  # 替换为你想要的新单词
        modified_lines.append(' '.join(words))

    with open(filename, 'w') as file:
        file.writelines(modified_lines)

# 调用函数来更改文件中每行的第一个单词
change_first_word('example.txt')