Tkinter : NameError:未定义名称'equation‘

Question

我有以下代码。我不能按下我创建的任何按钮，因为我得到了一个错误:每个按钮上都有NameError: name 'equation' is not defined。这有什么问题呢？我是Python的新手。我曾尝试将包含公式的这段代码放在不同的位置(在类外部，在main() func中)，但对我来说都不起作用

from tkinter import * 

expression = ""


class Calc(Frame):
    
    def __init__(self):
        super().__init__()

        self.UI()

    def UI(self):

        equation = StringVar()

        equation.set("0")

        large_font = ('Arial', 30)

        self.master.title("Kalkulator")
        self.pack(fill = BOTH, expand = 1)

        calc_txt = Entry(width = 204, font = large_font, bg = "gray", fg = "white", textvariable = equation)
        calc_txt.place(x = 0 , y = 0)

        percentage_btn = Button(width = 6, height = 2, text = "%", bg = "orange", fg = "white", borderwidth=2, relief="solid", command = lambda: press("%"))
        percentage_btn.place(x = 0, y = 49)

        sqr_btn = Button(width = 6, height = 2, text = "^", bg = "orange", fg = "white", borderwidth=2, relief="solid", command = lambda: press("**"))
        sqr_btn.place(x = 51, y = 49)

        sqr_root_btn = Button(width = 6, height = 2, text = "", bg = "orange", fg = "white", borderwidth=2, relief="solid", command = lambda: press(3))
        sqr_root_btn.place(x = 102, y = 49)

        multiply_btn = Button(width = 6, height = 2, text = "*", bg = "orange", fg = "white", borderwidth=2, relief="solid", command = lambda: press("*"))
        multiply_btn.place(x = 153, y = 49)

        divide_btn = Button(width = 6, height = 2, text = "/", bg = "orange", fg = "white", borderwidth=2, relief="solid", command = lambda: press("/"))
        divide_btn.place(x = 153, y = 89)

        add_btn = Button(width = 6, height = 2, text = "+", bg = "orange", fg = "white", borderwidth=2, relief="solid", command = lambda: press("+"))
        add_btn.place(x = 153, y = 129)

        substrct_btn = Button(width = 6, height = 2,  text = "-", bg = "orange", fg = "white", borderwidth=2, relief="solid", command = lambda: press("-"))
        substrct_btn.place(x = 153, y = 169)

        equal_btn = Button(width = 6, height = 2, text = "=", bg = "orange", fg = "white", borderwidth=2, relief="solid", command = equalpress)
        equal_btn.place(x = 153, y = 209)

        clear_btn = Button(width = 6, height = 2, text = "C", bg = "red", fg = "white", borderwidth=2, relief="solid", command = clear)
        clear_btn.place(x = 0, y = 209)

        dot_btn = Button(width = 6, height = 2,  text = ".", bg = "white", fg = "black", borderwidth=2, relief="solid", command = lambda: press("."))
        dot_btn.place(x = 51, y = 209)

        zero_btn = Button(width = 6, height = 2, text = "0", bg = "white", fg = "black", borderwidth=2, relief="solid", command = lambda: press(0))
        zero_btn.place(x = 102, y = 209)

        one_btn = Button(width = 6, height = 2, text = "1", bg = "white", fg = "black", borderwidth=2, relief="solid", command = lambda: press(1))
        one_btn.place(x = 0, y = 169)

        two_btn = Button(width = 6, height = 2, text = "2", bg = "white", fg = "black", borderwidth=2, relief="solid", command = lambda: press(2))
        two_btn.place(x = 51, y = 169)

        three_btn = Button(width = 6, height = 2, text = "3", bg = "white", fg = "black", borderwidth=2, relief="solid", command = lambda: press(3))
        three_btn.place(x = 102, y = 169)

        four_btn = Button(width = 6, height = 2, text = "4", bg = "white", fg = "black", borderwidth=2, relief="solid", command = lambda: press(4))
        four_btn.place(x = 0, y = 129)

        five_btn = Button(width = 6, height = 2, text = "5", bg = "white", fg = "black", borderwidth=2, relief="solid", command = lambda: press(5))
        five_btn.place(x = 51, y = 129)

        six_btn = Button(width = 6, height = 2, text = "6", bg = "white", fg = "black", borderwidth=2, relief="solid", command = lambda: press(6))
        six_btn.place(x = 102, y = 129)

        seven_btn = Button(width = 6, height = 2, text = "7", bg = "white", fg = "black", borderwidth=2, relief="solid", command = lambda: press(7))
        seven_btn.place(x = 0, y = 89)

        eight_btn = Button(width = 6, height = 2, text = "8", bg = "white", fg = "black", borderwidth=2, relief="solid", command = lambda: press(8))
        eight_btn.place(x = 51, y = 89)

        nine_btn = Button(width = 6, height = 2, text = "9", bg = "white", fg = "black", borderwidth=2, relief="solid", command = lambda: press(9))
        nine_btn.place(x = 102, y = 89)


def press(num): 
    
    global expression 
  
    expression = expression + str(num) 

    equation.set(expression)


def equalpress(): 
    
    try:

        global expression

        total = str(eval(expression))

        equation.set(total)

        expression = ""

    except:

        equation.set(" error ")
        expression = ""


def clear(): 
    global expression 
    expression = "" 
    equation.set("") 


def main():

    window = Tk()
    window.resizable(0,0)
    window.geometry("204x250")
    app = Calc()
    window.mainloop()


if __name__ == '__main__':
    main()

Answer 1

你需要在你的类中包含表达式变量和你的所有函数，然后给你想要“全局”的所有变量一个以self.开头的名称。如下所示：

from tkinter import *

class Calc(Frame):
    def __init__(self):
        super().__init__()
        self.UI()

    def UI(self):
        self.equation = StringVar()
        self.equation.set("0")
        self.expression = ''
        large_font = ('Arial', 30)
        calc_txt = Entry(width = 204, font = large_font, bg = "gray", fg = "white", textvariable = self.equation)
        calc_txt.place(x = 0 , y = 0)

        percentage_btn = Button(width = 6, height = 2, text = "%", bg = "orange", fg = "white", borderwidth=2, relief="solid", command = lambda: self.press("%"))
        percentage_btn.place(x = 0, y = 49)

    def press(self, num):
        self.expression = self.expression + str(num)
        self.equation.set(self.expression)

def main():
    window = Tk()
    window.resizable(0,0)
    window.geometry("204x250")
    app = Calc()
    window.mainloop()