Python 3.x 如何在python中进行动态列表更改？

Guy正在尝试为我的tk GUI创建页面，所以我在下面得到了这段代码，它工作得非常好，单击next按钮，它会得到前5个页面，直到100年底，反之亦然，单击prev按钮

import tkinter as tk
import math

items = [str(n) for n in range(100)]

page = 0
per_page = 5
n_pages = math.ceil(len(items) / per_page)


def update_list():
    print(page)
    start_index = int(page * per_page)
    end_index = int((page + 1) * per_page)
    items_in_page = items[start_index:end_index]
    view_text = "Page %d/%d: %s" % (page + 1, n_pages, ", ".join(items_in_page))

def change_page(delta):
    global page
    page = min(n_pages - 1, max(0, page + delta))
    update_list()

def prev_btn():
    change_page(-1)

def next_btn():
    change_page(+1)

win = tk.Tk()
win.title("clickers")
tk.Button(win, text="next", command=next_btn).pack()
tk.Button(win, text="prev", command=prev_btn).pack()
show = tk.Entry(win)
show.pack()
update_list()  # to initialize `show`
win.mainloop()

我想调整这部分代码

items = [str(n) for n in range(100)]

进入这样一个列表，并让它工作，只是切换它们不起作用

list_ = [1,2,3], [4,5,6], [7,8,9], [10,11,12], [13,14,15], [16,17,18]] 

items =[str(n) for n in list_]

因此，单击next按钮，它将返回前2行（任意数字选择）列表，反之亦然。完成后，请注意，此列表最初来自已选择的数据库的多行，而不仅仅是像我这样保存列表的某个变量，因此我需要关于如何直接使用循环获取前2行（2个列表）的帮助从数据库，并立即过去2行为prev按钮

import tkinter as tk
import math

items = [str(n) for n in range(100)]

page = 0
per_page = 5
n_pages = math.ceil(len(items) / per_page)


def update_list():
    print(page)
    start_index = int(page * per_page)
    end_index = int((page + 1) * per_page)
    items_in_page = items[start_index:end_index]
    view_text = "Page %d/%d: %s" % (page + 1, n_pages, ", ".join(items_in_page))

def change_page(delta):
    global page
    page = min(n_pages - 1, max(0, page + delta))
    update_list()

def prev_btn():
    change_page(-1)

def next_btn():
    change_page(+1)

win = tk.Tk()
win.title("clickers")
tk.Button(win, text="next", command=next_btn).pack()
tk.Button(win, text="prev", command=prev_btn).pack()
show = tk.Entry(win)
show.pack()
update_list()  # to initialize `show`
win.mainloop()