我看了你的代码，问题主要出在几个未处理的小错误上，导致点击按钮时触发了异常，直接让程序崩溃退出，界面也就跟着消失了。我们一步步来修复：

1. 未用self访问类成员变量 #

在renew方法处理退格（<-）的逻辑里，你写了：

self.Laststring = Laststring[:-1]

这里的Laststring没有加self.前缀，Python会把它当成局部变量，但你没提前定义过，所以点击退格按钮时会立刻抛出NameError，直接让程序崩溃。

修复方式：改成用self.访问类的成员变量：

self.Laststring = self.Laststring[:-1]

2. 退格时的索引越界问题 #

当self.Laststring为空列表时，执行self.Laststring[len(self.Laststring)-1]会触发IndexError——空列表没有索引-1对应的元素。我们需要先判断列表是否有内容再操作：

修改退格部分的代码：

if('<-' in self.s):
    # 先检查历史记录是否为空
    if self.Laststring:
        self.Laststring = self.Laststring[:-1]
        # 有历史记录就恢复最后一条，否则清空
        self.s = self.Laststring[-1] if self.Laststring else ''
        self.funcpr(self.s)
    else:
        self.s = ''
        self.funcpr(' ')
    self.show()

3. 重复创建Label导致的界面混乱 #

你的funcpr方法每次都新建一个Label来显示内容，而不是更新已有的Label。这不仅会导致旧Label被覆盖、界面混乱，还可能积累无用组件占用资源。

修复方式：
首先在__init__方法里提前创建好显示用的Label并保存为类成员：

def __init__(self):
    self.root = Tk()
    self.s = ''
    self.Laststring = []
    self.easymode = Frame(self.root,height=450,width=320,bg='pink')
    self.root.geometry('320x450')
    self.root.title('Calculator')
    # 新增：创建固定的显示Label，设置样式
    self.display_label = Label(self.easymode, text='', bg='white', justify=RIGHT, font=('Arial', 20))
    self.display_label.grid(row=0, column=0, columnspan=4, rowspan=2, sticky='nsew')

然后修改funcpr方法，只更新Label的文本内容：

def funcpr(self, t):
    self.display_label.config(text=t)

4. 计算逻辑的异常捕获优化 #

原来的Calculate方法直接用eval，如果输入了非法表达式会直接崩溃，我们给它加一层异常捕获：

def Calculate(self, string):
    try:
        return eval(string)
    except Exception as e:
        messagebox.showinfo('计算错误', f'输入表达式无效: {str(e)}')
        return ''

修复后的完整代码 #

from tkinter import *
from tkinter import messagebox

class EasyCalculator:
    def __init__(self):
        self.root = Tk()
        self.s = ''
        self.Laststring = []
        self.easymode = Frame(self.root, height=450, width=320, bg='pink')
        self.root.geometry('320x450')
        self.root.title('Calculator')
        # 创建固定的显示Label
        self.display_label = Label(self.easymode, text='', bg='white', justify=RIGHT, font=('Arial', 20))
        self.display_label.grid(row=0, column=0, columnspan=4, rowspan=2, sticky='nsew')

    def Calculate(self, string):
        try:
            return eval(string)
        except Exception as e:
            messagebox.showinfo('计算错误', f'输入表达式无效: {str(e)}')
            return ''

    def renew(self, strings):
        self.Laststring.append(self.s)
        self.s = self.s + strings
        if('<-' in self.s):
            if self.Laststring:
                self.Laststring = self.Laststring[:-1]
                self.s = self.Laststring[-1] if self.Laststring else ''
                self.funcpr(self.s)
            else:
                self.s = ''
                self.funcpr(' ')
            self.show()
        elif('=' not in self.s and 'AC' not in self.s):
            try:
                self.funcpr(self.s)
            except:
                messagebox.showinfo('Warning','Oops,something wrong!')
        elif('AC' in self.s):
            try:
                self.s = ''
                self.funcpr(' ')
            except:
                messagebox.showinfo('Warning','Oops,something wrong!')
        else:
            s2 = self.s.strip('=')
            result = self.Calculate(s2)
            if result != '':
                self.s = self.s + str(result)
                self.funcpr(self.s)
            self.s=''

    def funcpr(self, t):
        self.display_label.config(text=t)

    def CalWindows(self):
        #interface
        Button(self.easymode,text='1',command=lambda:self.renew('1')).place(x = 0,y = 200,width = 80,height = 50)
        Button(self.easymode,text='2',command=lambda:self.renew('2')).place(x = 80,y = 200,width = 80,height = 50)
        Button(self.easymode,text='3',command=lambda:self.renew('3')).place(x = 160,y = 200,width = 80,height = 50)
        Button(self.easymode,text='+',command=lambda:self.renew('+')).place(x = 240,y = 200,width = 80,height = 50)
        Button(self.easymode,text='4',command=lambda:self.renew('4')).place(x = 0,y = 250,width = 80,height = 50)
        Button(self.easymode,text='5',command=lambda:self.renew('5')).place(x = 80,y = 250,width = 80,height = 50)
        Button(self.easymode,text='6',command=lambda:self.renew('6')).place(x = 160,y = 250,width = 80,height = 50)
        Button(self.easymode,text='-',command=lambda:self.renew('-')).place(x = 240,y = 250,width = 80,height = 50)
        Button(self.easymode,text='7',command=lambda:self.renew('7')).place(x = 0,y = 300,width = 80,height = 50)
        Button(self.easymode,text='8',command=lambda:self.renew('8')).place(x = 80,y = 300,width = 80,height = 50)
        Button(self.easymode,text='9',command=lambda:self.renew('9')).place(x = 160,y = 300,width = 80,height = 50)
        Button(self.easymode,text='X',command=lambda:self.renew('*')).place(x = 240,y = 300,width = 80,height = 50)
        Button(self.easymode,text='AC',command=lambda:self.renew('AC')).place(x = 0,y = 350,width = 80,height = 50)
        Button(self.easymode,text='<-',command=lambda:self.renew('<-')).place(x = 80,y = 350,width = 80,height = 50)
        Button(self.easymode,text='%',command=lambda:self.renew('%')).place(x = 160,y = 350,width = 80,height = 50)
        Button(self.easymode,text='/',command=lambda:self.renew('/')).place(x = 240,y = 350,width = 80,height = 50)
        Button(self.easymode,text='.',command=lambda:self.renew('.')).place(x = 0,y = 400,width = 80,height = 50)
        Button(self.easymode,text='0',command=lambda:self.renew('0')).place(x = 80,y = 400,width = 80,height = 50)
        Button(self.easymode,text='=',command=lambda:self.renew('='),bg='Orange').place(x = 160,y = 400,width = 160,height = 50)

    def show(self):
        self.easymode.pack()
        self.CalWindows()
        self.root.mainloop()

if __name__=='__main__':
    Calculator1 = EasyCalculator()
    Calculator1.show()

现在运行代码，点击按钮就不会出现界面消失的问题了，显示逻辑也更稳定~

内容的提问来源于stack exchange，提问作者MeilinZ