Python製作一個簡單的計算器

from tkinter import *
from tkinter import ttk

class Calculator():
    calc_value = 0.0

    div_trigger = False
    mult_trigger = False
    add_trigger = False
    sub_trigger = False
    def button_press(self,value):
        entry_val = self.number_entry.get()
        if value == 'AC':

            self.number_entry.delete(0,'end')
        else:
            entry_val +=value
            self.number_entry.delete(0,'end')
            self.number_entry.insert(0,entry_val)
    def isfloat(self,str_val):
        try:
            float(str_val)
            return True
        except ValueError:
            return False

    def math_button_press(self,value):
        if self.isfloat(str(self.number_entry.get())):
            self.div_trigger = False
            self.mult_trigger = False
            self.add_trigger = False
            self.sub_trigger = False            

        self.calc_value=float(self.entry_value.get())
        if value == '/':
            print('/ Pressed')
            self.div_trigger = True
        elif value == '*':
            print('* Pressed')
            self.mult_trigger = True
        elif value == '+':
            print('+ Pressed')
            self.add_trigger = True
        else:
            print('- Pressed')
            self.sub_trigger = True


        self.number_entry.delete(0,'end')

    def equal_button_press(self):
        if self.add_trigger or self.sub_trigger or self.mult_trigger or self.div_trigger:
            if self.add_trigger:
                solution = self.calc_value+float(self.entry_value.get())
            elif self.sub_trigger:
                solution = self.calc_value-float(self.entry_value.get())
            elif self.mult_trigger:
                solution = self.calc_value*float(self.entry_value.get())
            else:
                solution = self.calc_value/float(self.entry_value.get())

            self.number_entry.delete(0,'end')
            self.number_entry.insert(0,solution)


    def __init__(self,root):
        self.entry_value = StringVar(root,value='')
        root.title('Calculator')
        root.geometry('430x220')
        root.resizable(width=False,height=False)
        style =ttk.Style()
        style.configure('TButton',font = 'serif 15',padding = 6)
        style.configure('TEntry',font='Serif 18',padding=6)
        self.number_entry = ttk.Entry(root,textvariable=self.entry_value,
                                      width=60)

        self.number_entry.grid(row=0,columnspan=4)
        #--------------1---------------------------
        self.button7=ttk.Button(root,text='7',
                command=lambda:self.button_press('7')).grid(row=1,column=0)

        self.button8=ttk.Button(root,text='8',
                command=lambda:self.button_press('8')).grid(row=1,column=1)

        self.button9=ttk.Button(root,text='9',
                command=lambda:self.button_press('9')).grid(row=1,column=2)

        self.button_div=ttk.Button(root,text='/',
                command=lambda:self.math_button_press('/')).grid(row=1,column=3)
        #---------------2----------------------------
        self.button4=ttk.Button(root,text='4',
                command=lambda:self.button_press('4')).grid(row=2,column=0)

        self.button5=ttk.Button(root,text='5',
                command=lambda:self.button_press('5')).grid(row=2,column=1)

        self.button6=ttk.Button(root,text='6',
                command=lambda:self.button_press('6')).grid(row=2,column=2)

        self.button_mul=ttk.Button(root,text='*',
                command=lambda:self.math_button_press('*')).grid(row=2,column=3)
        #---------------3--------------------------
        self.button1=ttk.Button(root,text='1',
                command=lambda:self.button_press('1')).grid(row=3,column=0)

        self.button2=ttk.Button(root,text='2',
                command=lambda:self.button_press('2')).grid(row=3,column=1)

        self.button3=ttk.Button(root,text='3',
                command=lambda:self.button_press('3')).grid(row=3,column=2)

        self.button_add=ttk.Button(root,text='+',
                command=lambda:self.math_button_press('+')).grid(row=3,column=3)
        #---------------4----------------------
        self.button_clear=ttk.Button(root,text='AC',
                command=lambda:self.button_press('AC')).grid(row=4,column=0)

        self.button0=ttk.Button(root,text='0',
                command=lambda:self.button_press('0')).grid(row=4,column=1)

        self.button_equal=ttk.Button(root,text='=',
                command=lambda:self.equal_button_press()).grid(row=4,column=2)

        self.button_sub=ttk.Button(root,text='-',
                command=lambda:self.math_button_press('-')).grid(row=4,column=3)        

root = Tk()
calc=Calculator(root)
root.mainloop()