使用python的tkinter制作简单计算器

计算器只有加、减、乘、除、取反
代码中有详细注释
将计算器封装成了一个类

效果图：

import tkinter as tk

class App:
    def __init__(self):
        self.root = tk.Tk()
        self.root.title('小小计算器')
        # 指定窗口大小和默认所处位置
        self.root.geometry("295x280+150+150")
        self.root['background'] = '#ffffff'

        # 存放按键输入的元素
        self.mylist = []
        # 在界面中要显示的内容
        self.result_num = tk.StringVar()
        self.result_num.set(0)
        self.layout()

        self.root.mainloop()


    def put(self,x):
        '''点击数字后，将按键输入的内容保存在列表 mylist 中，使用join拼接为字符串显示出来'''
        self.mylist.append(x)
        self.result_num.set(''.join(self.mylist))


    def delete(self):
        '''清空按钮功能'''
        self.mylist.clear()
        self.result_num.set(0)


    def back(self):
        '''删除按钮功能，删除一个数字或运算符'''
        if len(self.mylist) > 0:
            del self.mylist[-1]
            self.result_num.set(self.mylist)


    def calculation(self):
        '''运算按钮'''
        expression = ''.join(self.mylist)
        result = eval(expression)
        self.result_num.set(result)
        # 计算出结果后清空数据列表，仅存储当前计算结果
        self.mylist.clear()
        # join将列表中的元素拼接为字符串，列表元素必须全为str型
        self.mylist.append(str(result))


    def operate(self,operator):
        '''
        点击运算操作符后判断前一个按键是否为操作符
        若前一个按键为操作符，则修改上一个操作符为当前操作符
        否则将当前操作符加入显示列表
        '''

        if len(self.mylist) > 0:
            if self.mylist[-1] in ['+', '-', '*', '/','.']:
                self.mylist[-1] = operator
            else:
                self.mylist.append(operator)

            self.result_num.set(''.join(self.mylist))


    def inverse(self):
        '''若前一个按键是一个数字，则将这个数字转换为负数'''
        if len(self.mylist) > 0 and self.mylist[-1] not in ['+', '-', '*', '/','.']:
            self.mylist[-1] = str(-int(self.mylist[-1]))
            self.result_num.set(''.join(self.mylist))

    def layout(self):
        # 网格的第一行为显示面板
        # 显示按键输入内容与运算结果的面板
        label = tk.Label(self.root, textvariable=self.result_num, width=20, height=2,
                        justify='left', anchor='se', bg='#ffffff', font=('宋体', 20))
        label.grid(row=0, column=0, padx=4, pady=4, columnspan=4)


        # 第二行开始为运算符
        button_clear = tk.Button(self.root, text='C', width=5, font=(
            '宋体', 16), bg='#C0C0C0', command=self.delete)
        button_clear.grid(row=1, column=0, padx=4, pady=4)
        # 删除键
        button_back = tk.Button(self.root, text='←', width=5, font=(
            '宋体', 16), bg='#C0C0C0', command=self.back)
        button_back.grid(row=1, column=1, padx=4, pady=4)
        # 除法
        button_div = tk.Button(self.root, text='/', width=5, font=('宋体', 16),
                            bg='#C0C0C0', command=lambda: self.operate('/'))
        button_div.grid(row=1, column=2, padx=4, pady=4)
        # 乘法
        button_mult = tk.Button(self.root, text='*', width=5, font=('宋体', 16),
                                bg='#C0C0C0', command=lambda: self.operate('*'))
        button_mult.grid(row=1, column=3, padx=4, pady=4)

        # 第三行开始为数字

        # 第三行
        button_seven = tk.Button(self.root,text=7, width=5, font=(
            '宋体', 16), bg='#FFDEAD', command=lambda: self.put('7'))
        button_seven.grid(row=2, column=0, padx=4)

        button_eight = tk.Button(self.root,text=8, width=5, font=(
            '宋体', 16), bg='#FFDEAD', command=lambda: self.put('8'))
        button_eight.grid(row=2, column=1, padx=4)

        button_nine = tk.Button(self.root,text=9, width=5, font=(
            '宋体', 16), bg='#FFDEAD', command=lambda: self.put('9'))
        button_nine.grid(row=2, column=2, padx=4)

        button_sub = tk.Button(self.root, text='-', width=5, font=('宋体', 16),
                            bg='#C0C0C0', command=lambda: self.operate('-'))
        button_sub.grid(row=2, column=3, padx=4, pady=4)

        # 第四行
        button_four = tk.Button(self.root,text=4, width=5, font=(
            '宋体', 16), bg='#FFDEAD', command=lambda: self.put('4'))
        button_four.grid(row=3, column=0, padx=4)

        button_five = tk.Button(self.root,text=5, width=5, font=(
            '宋体', 16), bg='#FFDEAD', command=lambda: self.put('5'))
        button_five.grid(row=3, column=1, padx=4)

        button_six = tk.Button(self.root,text=6, width=5, font=('宋体', 16),
                            bg='#FFDEAD', command=lambda: self.put('6'))
        button_six.grid(row=3, column=2, padx=4)

        button_add = tk.Button(self.root, text='+', width=5, font=('宋体', 16),
                            bg='#C0C0C0', command=lambda: self.operate('+'))
        button_add.grid(row=3, column=3, padx=4, pady=4)

        # 第五行
        button_one = tk.Button(self.root, text=1, width=5, font=(
            '宋体', 16), bg='#FFDEAD', command=lambda: self.put('1'))
        button_one.grid(row=4, column=0, padx=4)

        button_two = tk.Button(self.root, text=2, width=5, font=(
            '宋体', 16), bg='#FFDEAD', command=lambda: self.put('2'))
        button_two.grid(row=4, column=1, padx=4)

        button_three = tk.Button(self.root, text=3, width=5, font=(
            '宋体', 16), bg='#FFDEAD', command=lambda: self.put('3'))
        button_three.grid(row=4, column=2, padx=4)

        button_equal = tk.Button(self.root, text='=', width=5, height=3, font=(
            '宋体', 16), bg='#C0C0C0', command=self.calculation)
        button_equal.grid(row=4, column=3, padx=4, rowspan=5)

        # 第六行
        # 取反，用来表示相反数和负数
        button_not = tk.Button(self.root, text='+/-', width=5,
                            font=('宋体', 16), bg='#FFDEAD', command=self.inverse)
        button_not.grid(row=5, column=0, padx=4)

        button_zero = tk.Button(self.root, text=0, width=5, font=(
            '宋体', 16), bg='#FFDEAD', command=lambda: self.put('0'))
        button_zero.grid(row=5, column=1, padx=4)

        # 小数点
        button_pot = tk.Button(self.root, text='.', width=5, font=(
            '宋体', 16), bg='#FFDEAD', command=lambda: self.put('.'))
        button_pot.grid(row=5, column=2, padx=4, pady=4)



app = App()