简易计算器

参考：https://gitee.com/cx20201316/text/blob/master/GUI.py
`import tkinter as tk

class jsj:
def init(self):
self.root = tk.Tk()
self.root.title('简易计算器')
self.mylist = []
self.result = tk.StringVar()
self.result.set(0)
self.layout()

    self.root.mainloop()

def put(self, x):
    self.mylist.append(x)
    self.result.set(''.join(self.mylist))

def delete(self):
    self.mylist.clear()
    self.result.set(0)

def back(self):
    if len(self.mylist) > 0:
        del self.mylist[-1]
        self.result.set(self.mylist)

def calculation(self):
    expression = ''.join(self.mylist)
    result = eval(expression)
    self.result.set(result)
    self.mylist.clear()
    self.mylist.append(str(result))

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

def layout(self):
    label = tk.Label(self.root, textvariable=self.result,
                     width=20, height=2, justify='left', anchor='se')
    label.grid(row=0, column=0, padx=4, pady=4, columnspan=4)
    button_clear = tk.Button(
        self.root, text='C', width=12, command=self.delete)
    button_clear.grid(row=1, column=0, columnspan=2, padx=4, pady=4)
    button_back = tk.Button(self.root, text='←',
                            width=5, command=self.back)
    button_back.grid(row=1, column=2, padx=4, pady=4)
    button_div = tk.Button(self.root, text='/', width=5,
                           command=lambda: self.operate('/'))
    button_div.grid(row=4, column=3, padx=4, pady=4)
    button_mult = tk.Button(self.root, text='*',
                            width=5, command=lambda: self.operate('*'))
    button_mult.grid(row=3, column=3, padx=4, pady=4)
    button_seven = tk.Button(
        self.root, text=7, width=5, command=lambda: self.put('7'))
    button_seven.grid(row=2, column=0, padx=4)
    button_eight = tk.Button(
        self.root, text=8, width=5, command=lambda: self.put('8'))
    button_eight.grid(row=2, column=1, padx=4)
    button_nine = tk.Button(
        self.root, text=9, width=5, command=lambda: self.put('9'))
    button_nine.grid(row=2, column=2, padx=4)
    button_sub = tk.Button(self.root, text='-', width=5,
                           command=lambda: self.operate('-'))
    button_sub.grid(row=2, column=3, padx=4, pady=4)
    button_four = tk.Button(
        self.root, text=4, width=5, command=lambda: self.put('4'))
    button_four.grid(row=3, column=0, padx=4)
    button_five = tk.Button(
        self.root, text=5, width=5, command=lambda: self.put('5'))
    button_five.grid(row=3, column=1, padx=4)
    button_six = tk.Button(self.root, text=6, width=5,
                           command=lambda: self.put('6'))
    button_six.grid(row=3, column=2, padx=4)
    button_add = tk.Button(self.root, text='+', width=5,
                           command=lambda: self.operate('+'))
    button_add.grid(row=1, column=3, padx=4, pady=4)
    button_one = tk.Button(self.root, text=1, width=5,
                           command=lambda: self.put('1'))
    button_one.grid(row=4, column=0, padx=4)
    button_two = tk.Button(self.root, text=2, width=5,
                           command=lambda: self.put('2'))
    button_two.grid(row=4, column=1, padx=4)
    button_three = tk.Button(
        self.root, text=3, width=5, command=lambda: self.put('3'))
    button_three.grid(row=4, column=2, padx=4)
    button_equal = tk.Button(
        self.root, text='=', width=12, command=self.calculation)
    button_equal.grid(row=5, column=2, columnspan=2, padx=4, rowspan=5)
    button_zero = tk.Button(
        self.root, text=0, width=5, command=lambda: self.put('0'))
    button_zero.grid(row=5, column=1, padx=4)
    button_pot = tk.Button(self.root, text='.', width=5,
                           command=lambda: self.put('.'))
    button_pot.grid(row=5, column=0, padx=4, pady=4)

jsj()
`