Tkinter仅显示段落的最后三行

import tkinter as tk

def show_last_three_lines(paragraph):
    root = tk.Tk()
    text_box = tk.Text(root)
    text_box.pack()

    # 插入文本内容
    text_box.insert(tk.END, paragraph)

    # 获取行数
    line_count = int(text_box.index(tk.END).split('.')[0])

    # 获取最后三行的起始索引
    start_index = f"{line_count - 2}.0"

    # 获取最后三行的文本内容
    last_three_lines = text_box.get(start_index, tk.END)

    # 清空文本框
    text_box.delete(1.0, tk.END)

    # 显示最后三行的文本内容
    text_box.insert(tk.END, last_three_lines)

    root.mainloop()

# 示例用法
paragraph = """
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Pellentesque euismod justo nec nunc tincidunt, id lacinia nisl tincidunt.
Sed euismod, nunc id aliquet tincidunt, mauris nunc tincidunt nunc, id tincidunt nunc nunc nec nunc.
Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia curae;
Sed euismod, nunc id aliquet tincidunt, mauris nunc tincidunt nunc, id tincidunt nunc nunc nec nunc.
"""

show_last_three_lines(paragraph)