向Python GUI计算器添加退格按钮

我正在用tkinter用python制作一个GUI计算器。计算器工作得非常好，现在我想添加一个退格函数，以便它清除显示器上的最后一个数字。例如，321将变成32。我已经尝试过定义函数“backspace”和“bind_all”方法，但我不太确定它们是如何工作的，从而导致错误消息。如果有人能告诉我怎么做并解释一下，我将不胜感激

非常感谢您的帮助

from tkinter import *

def quit ():
root.destroy()
# the main class
class Calc():
def __init__(self):
    self.total = 0
    self.current = ""
    self.new_num = True
    self.op_pending = False
    self.op = ""
    self.eq = False

#setting the variable when the number is pressed
def num_press(self, num):
    self.eq = False
    temp = text_box.get()
    temp2 = str(num)
    if self.new_num:
        self.current = temp2
        self.new_num = False

    else:
        if temp2 == '.':
            if temp2 in temp:
                return
        self.current = temp + temp2
    self.display(self.current)



# event=None to use function in command= and in binding
def clearLastDigit(self, event=None):
    current = self.text_box.get()[:-1]
    self.text_box.delete(0, END)
    self.text_box.current(INSERT, text)


def calc_total(self):
    self.eq = True
    self.current = float(self.current)
    if self.op_pending == True:
        self.do_sum()
    else:
        self.total = float(text_box.get())

#setting up the text display area
def display(self, value):
    text_box.delete(0, END)
    text_box.insert(0, value)


#Opperations Button
def do_sum(self):
    if self.op == "add":
        self.total += self.current
    if self.op == "minus":
        self.total -= self.current
    if self.op == "times":
        self.total *= self.current
    if self.op == "divide":
        self.total /= self.current
    self.new_num = True
    self.op_pending = False
    self.display(self.total)

def operation(self, op):
    self.current = float(self.current)
    if self.op_pending:
        self.do_sum()
    elif not self.eq:
        self.total = self.current
    self.new_num = True
    self.op_pending = True
    self.op = op
    self.eq = False

#Clear last entry
def cancel(self):
    self.eq = False
    self.current = "0"
    self.display(0)
    self.new_num = True

#Clear all entries
def all_cancel(self):
    self.cancel()
    self.total = 0

#backspace button
def backspace(self):
    self.cancel()
    self.display(len(self.text_box.get())-1)


#Changing the Sign (+/-)
def sign(self):
    self.eq = False
    self.current = -(float(text_box.get()))
    self.display(self.current)



#Global Varibles that are used within Attributes
sum1 = Calc()
root = Tk()
calc = Frame(root)
calc.grid()

#Creating the window for the calculator
root.title("Calculator")
text_box = Entry(calc, justify=RIGHT)
text_box.grid(row = 0, column = 0, columnspan = 3, pady = 5)
text_box.insert(0, "0")

#buttons 1-9 (Displayed row by row)
numbers = "789456123"
i = 0
bttn = []
for j in range(1,4):
for k in range(3):
    bttn.append(Button(calc, text = numbers[i], width= 5, height = 2, bg="#fe0000"))
    bttn[i].grid(row = j, column = k)
    bttn[i]["command"] = lambda x = numbers[i]: sum1.num_press(x)
    i += 1
#button 0
bttn_0 = Button(calc, text = "0", width= 5, height = 2, bg="#fe0000")
bttn_0["command"] = lambda: sum1.num_press(0)
bttn_0.grid(row = 4, column = 1, pady = 5)

#button / (Divide)
bttn_div = Button(calc, text = chr(247), width= 5, height = 2, bg="#00b0f0" )
bttn_div["command"] = lambda: sum1.operation("divide")
bttn_div.grid(row = 1, column = 3, pady = 5)

#button x (Times)
bttn_mult = Button(calc, text = "x", width= 5, height = 2, bg="#00b0f0")
bttn_mult["command"] = lambda: sum1.operation("times")
bttn_mult.grid(row = 2, column = 3, pady = 5)

#button - (Minus)
minus = Button(calc, text = "-", width= 5, height = 2, bg="#00b0f0")
minus["command"] = lambda: sum1.operation("minus")
minus.grid(row = 4, column = 3, pady = 5)

#button + (Plus)
add = Button(calc, text = "+", width= 5, height = 2, bg="#00b0f0")
add["command"] = lambda: sum1.operation("add")
add.grid(row = 3, column = 3, pady = 5)

#button + or - (Plus/minus)
neg= Button(calc, text = "+/-", width= 5, height = 2, bg="#7030a0")
neg["command"] = sum1.sign
neg.grid(row = 5, column = 0, pady = 5)

#button Clear (Clear)
clear = Button(calc, text = "C", width= 5, height = 2, bg="yellow")
clear["command"] = sum1.cancel
clear.grid(row = 5, column = 1, pady = 5)

#button All Clear ( All Clear)
all_clear = Button(calc, text = "CE", width= 5, height = 2, bg="yellow")
all_clear["command"] = sum1.all_cancel
all_clear.grid(row = 5, column = 2, pady = 5)

#button . (Decimal)
point = Button(calc, text = ".", width= 5, height = 2, bg="#c00000")
point["command"] = lambda: sum1.num_press(".")
point.grid(row = 4, column = 0, pady = 5)

#button = (Equals)
equals = Button(calc, text = "=", width= 5, height = 2, bg="#7030a0")
equals["command"] = sum1.calc_total
equals.grid(row = 4, column = 2, pady = 5)

#button Quit
quit_bttn = Button(calc, text ="Quit", width=5, height = 2, bg="green")
quit_bttn["command"] = quit
quit_bttn.grid(row = 5, column = 3)

#button BackSpace
backspace_bttn = Button(calc, text = "Backspace", width= 15, height = 2, bg="yellow")
backspace_bttn["command"] = sum1.backspace
backspace_bttn.grid(row = 6, column = 0, columnspan = 4)


root.mainloop()

---

显示错误消息-可能您的参数数量有问题

bind_all

用两个参数调用函数

backspace（self，event）

，

command

只用一个参数调用函数

backspace（self）

请在

def clearLastDigit（self，event=None）之前的代码中查看我的注释：

要使用

backspace

和

command=

您需要

def backspace(self):
    self.cancel()
    self.display(len(self.text_box.get())-1)

def backspace(self, event):
    self.cancel()
    self.display(len(self.text_box.get())-1)

要使用

backspace

和

bind\u all

您需要的

def backspace(self):
    self.cancel()
    self.display(len(self.text_box.get())-1)

def backspace(self, event):
    self.cancel()
    self.display(len(self.text_box.get())-1)

顺便说一下：

len（self.text\u box.get（））-1

为文本长度减去1。如果需要分类器文本（321->32），请使用

self.display（self.text\u box.get（）[：-1]）

---

请参见答案中带退格的计算器

---

编辑：对于

命令

您只需更改

退格（self）

def backspace(self):
    text = text_box.get()[:-1]
    if text == "":
        text = "0"
    self.current = text
    self.display( text )

---

在某些特殊情况下，可能需要进行一些其他更改才能获得正确的结果。

@furas这是我在backspace self.display（len（self.text\u box.get（））-1）AttributeError:Calc对象在oryginal版本中没有属性“text\u box”（请参阅我答案中的链接）所有按钮都在类内，有

self.text\u box

，但所有按钮都在类外，所以你有

text\u box

，而不是

self.text\u box

如果你有类外的代码，你应该放弃使用类，并将所有函数（经过一些修改）从类移到类外。有人可能会问：“为什么你把一些函数放在类内而把其他函数放在类外？你真的知道如何使用类吗？”谢谢你的回答。因此，如果我要使用命令方法，我将如何操作。对于命令，您需要更改

backspace（）

请参阅答案中的新代码。非常感谢！代码现在运行良好。你提到了一些关于修课的事情，你能解释一下我能做些什么来提高它吗。ThanksTeacher可以问“为什么你只把部分代码放在类中？为什么你不把所有代码都放在类中？”最好的解决方案是把所有代码都放在类中-参见我的答案中的示例-所有代码都在类中，除了我创建类实例的最后一行，我使用

run（）

启动

mainloop

。因此，要把所有代码都放在同一个类中，是否将属性中使用的所有全局变量缩进到下？