NameError：tkinter 中未定义名称“f_num”

如何解决NameError：tkinter 中未定义名称“f_num”

我正在尝试对我的计算器项目进行编程以执行操作。它可以执行加法，我想要它执行剩下的四个（减号、乘法、除法、幂）但我因为这个错误而卡住了：

C:\Users\Admin\PycharmProjects\venv\Scripts\python.exe 
   "C:/Users/Admin/PycharmProjects/pythonProject/Calculator GUI v1.0.py"
   Exception in Tkinter callback
   Traceback (most recent call last):
    File "C:\Users\Admin\python3.9\lib\tkinter\__init__.py",line 1892,in __call__
    return self.func(*args)
    File "C:\Users\Admin\PycharmProjects\pythonProject\Calculator GUI v1.0.py",line 32,in 
    button_subtract
     e.insert(0,f_num + int(second_number))
    NameError: name 'f_num' is not defined

   Process finished with exit code 0

我的代码：

import tkinter as Tk
from tkinter import *

root_var = Tk()
root_var.title("Calculator")

e = Entry(root_var,width=25,borderwidth=5)
e.grid(row=0,column=0,columnspan=3,padx=10,pady=10)

def button_click(number=None):

#e.delete(0,END)
current = e.get()
e.delete(0,END)
e.insert(0,str(current) + str(number) )

def button_clear():
e.delete(0,END)


def button_add():
first_number = e.get()
global f_num
f_num = int(first_number)
e.delete(0,END)


def button_subtract():
second_number = e.get()
e.delete(0,f_num + int(second_number))


def button_multiply():
third_number = e.get()
e.delete(0,f_num + int(third_number))



def button_divide():
fourth_number = e.get()
e.delete(0,f_num + int(fourth_number))



def button_exponents():
fifth_number = e.get()
e.delete(0,f_num + int(fifth_number))

def button_equal():
sixth_number = e.get()
e.delete(0,f_num + int(sixth_number))

 button_1 = Button(root_var,text="1",padx=50,pady=10,command=lambda: button_click(1))
 button_2 = Button(root_var,text="2",command=lambda: button_click(2))
 button_3 = Button(root_var,text="3",command=lambda: button_click(3))
 button_4 = Button(root_var,text="4",command=lambda: button_click(4))
 button_5 = Button(root_var,text="5",command=lambda: button_click(5))
 button_6 = Button(root_var,text="6",command=lambda: button_click(6))
 button_7 = Button(root_var,text="7",command=lambda: button_click(7))
 button_8 = Button(root_var,text="8",command=lambda: button_click(8))
 button_9 = Button(root_var,text="9",command=lambda: button_click(9))
 button_0 = Button(root_var,text="0",command=lambda: button_click(0))

 button_addition = Button(root_var,text="+",command=button_add)
 button_subtraction = Button(root_var,text="-",command=button_subtract)
 button_multiplication = Button(root_var,text="*",command=button_multiply)
 button_division = Button(root_var,text="/",command=button_divide)
 button_exponents = Button(root_var,text="^",command=button_exponents)

 button_equals = Button(root_var,text="=",command=button_equal)

 button_clear = Button(root_var,text="C",command=button_clear)

  button_1.grid(row=3,column=2)
  button_2.grid(row=3,column=1)
  button_3.grid(row=3,column=0)

  button_4.grid(row=2,column=2)
  button_5.grid(row=2,column=1)
  button_6.grid(row=2,column=0)

  button_7.grid(row=1,column=2)
  button_8.grid(row=1,column=1)
  button_9.grid(row=1,column=0)

  button_0.grid(row=4,column=0)
  button_addition.grid(row=4,column=1)
  button_subtraction.grid(row=4,column=2)

  button_multiplication.grid(row=5,column=0)
  button_division.grid(row=5,column=1)
  button_exponents.grid(row=5,column=2)

  button_equals.grid(row=6,column=0)
  button_clear.grid(row=6,column=1)


  root_var.mainloop()

加法操作有效。我希望其他操作也能够执行各自的任务。

解决方法

点击其中一个操作符时，需要将当前输入的数字保存到f_num，将操作符保存到另一个变量中，例如opr。

然后当点击=时，根据保存的opr、f_num和当前输入值进行计算。

以下是基于您的代码的示例：

from tkinter import *

root_var = Tk()
root_var.title("Calculator")

e = Entry(root_var,width=25,borderwidth=5)
e.grid(row=0,column=0,columnspan=3,padx=10,pady=10)

f_num = opr = None

def button_click(number=None):
    current = e.get()
    e.delete(0,END)
    e.insert(0,current+str(number))

def button_opr(op):
    global f_num,opr
    # save the first number and operator
    try:
        f_num = int(e.get())
        opr = op
        # clear the entry
        e.delete(0,END)
    except Exception as ex:
        print(ex)

def button_clear():
    global f_num,opr
    e.delete(0,END)
    # reset first number and operator
    f_num = opr = None

def button_equal():
    global f_num,opr
    if f_num and opr:
        try:
            current = int(e.get())
            e.delete(0,END)
            if opr == "+":
                e.insert(0,f_num+current)
            elif opr == "-":
                e.insert(0,f_num-current)
            elif opr == "*":
                e.insert(0,f_num*current)
            elif opr == "/":
                e.insert(0,f_num/current)
            elif opr == "^":
                e.insert(0,f_num**current)
        except Exception as ex:
            print(ex)
    # reset first number and operator
    f_num = opr = None

button_1 = Button(root_var,text="1",padx=50,pady=10,command=lambda: button_click(1))
button_2 = Button(root_var,text="2",command=lambda: button_click(2))
button_3 = Button(root_var,text="3",command=lambda: button_click(3))
button_4 = Button(root_var,text="4",command=lambda: button_click(4))
button_5 = Button(root_var,text="5",command=lambda: button_click(5))
button_6 = Button(root_var,text="6",command=lambda: button_click(6))
button_7 = Button(root_var,text="7",command=lambda: button_click(7))
button_8 = Button(root_var,text="8",command=lambda: button_click(8))
button_9 = Button(root_var,text="9",command=lambda: button_click(9))
button_0 = Button(root_var,text="0",command=lambda: button_click(0))

button_addition = Button(root_var,text="+",command=lambda: button_opr("+"))
button_subtraction = Button(root_var,text="-",command=lambda: button_opr("-"))
button_multiplication = Button(root_var,text="*",command=lambda: button_opr("*"))
button_division = Button(root_var,text="/",command=lambda: button_opr("/"))
button_exponents = Button(root_var,text="^",command=lambda: button_opr("^"))
button_equals = Button(root_var,text="=",command=button_equal)
button_clear = Button(root_var,text="C",command=button_clear)

button_1.grid(row=3,column=2,sticky="ew")
button_2.grid(row=3,column=1,sticky="ew")
button_3.grid(row=3,sticky="ew")
button_4.grid(row=2,sticky="ew")
button_5.grid(row=2,sticky="ew")
button_6.grid(row=2,sticky="ew")
button_7.grid(row=1,sticky="ew")
button_8.grid(row=1,sticky="ew")
button_9.grid(row=1,sticky="ew")
button_0.grid(row=4,sticky="ew")

button_addition.grid(row=4,sticky="ew")
button_subtraction.grid(row=4,sticky="ew")
button_multiplication.grid(row=5,sticky="ew")
button_division.grid(row=5,sticky="ew")
button_exponents.grid(row=5,sticky="ew")
button_equals.grid(row=6,sticky="ew")
button_clear.grid(row=6,sticky="ew")

root_var.mainloop()

您可以创建一个类，然后将所有函数放入该类中并声明 f_num 为 self.f_num。

如果你不知道如何使用类，你也可以尝试这样的事情：

f_num = 0

def button_add():
    global f_num
    first_number = 10
    f_num = first_number
    


def button_subtract():
    global f_num
    second_number = 20
    print(f_num + second_number)

button_add()
button_subtract()

print(f_num)

在函数外声明f_num，然后在函数内对 f_num执行所有操作。（添加global否则f_num的值不会改变）