Arranjos e Combinações matemáticas usando Tkinter

from tkinter import *
from tkinter import ttk

root=Tk()
class app():
    def __init__(self):
        self.root = root
        self.janela()
        self.frames_da_janela()
        self.widgets_frame1()
        self.Menus()
        self.root.mainloop()
    def janela(self):
        self.root.title("Arranjos e Combinações")
        self.root.configure(background='#1e3743')
        self.root.geometry("450x200")
        self.root.resizable(False, False)
    def frames_da_janela(self):
        self.frame_1 = Frame(self.root, bd=4, bg='#dfe3ee', 
                             highlightbackground='#759fe6', highlightthickness=2)
        self.frame_1.place(relx=0.02, rely=0.02, relwidth=0.96, 
                           relheight=0.96)
    def widgets_frame1(self):
        self.abas = ttk.Notebook(self.frame_1)
        self.arr = Frame(self.abas)
        self.cob = Frame(self.abas)
        self.arr.configure(background="#dfe3ee")
        self.cob.configure(background="#dfe3ee")
        self.abas.add(self.arr, text="Arranjos")
        self.abas.add(self.cob, text="Combinações ")
        self.abas.place(relx=0, rely=0, relwidth=0.98
                        , relheight=0.98)
        # n elementos tomados
        self.n = IntVar()
        self.lb_n = Label(self.arr, text="N", bg='#dfe3ee',
                          fg='#107db2')
        self.lb_n.place(relx=0.3, rely=0.05)
        self.n_entry = Entry(self.arr, textvariable=self.n)
        self.n_entry.place(relx=0.4, rely=0.05, relwidth=0.1)
        # k elementos tomados
        self.k = IntVar()
        self.lb_k = Label(self.arr, text="K", bg='#dfe3ee', fg='#107db2')
        self.lb_k.place(relx=0.3, rely=0.25)
        self.k_entry = Entry(self.arr, textvariable=self.k)
        self.k_entry.place(relx=0.4, rely=0.25, relwidth=0.1)
        self.bt_calcular1 = Button(self.arr, text="Calcular", bd=2, 
                                   bg='#107db2', fg='white',
                                   font=('verdana', 8, 'bold'),
                                   command=self.butaoclickarr)
        #a
        self.bt_calcular1.place(relx=0.6, rely=0.15, relwidth=0.2, 
                                relheight=0.25)
        # Resultado
        self.resultado = StringVar()
        self.resultado2 = Label(self.arr, textvariable=self.resultado)
        self.resultado2.place(relx=0.4, rely=0.6, relwidth=0.1)
        #Combinação
        # n elementos tomados
        self.n1 = IntVar()
        self.lb_n1 = Label(self.cob, text="N", bg='#dfe3ee', fg='#107db2')
        self.lb_n1.place(relx=0.3, rely=0.05)
        self.n1_entry = Entry(self.cob, textvariable=self.n1)
        self.n1_entry.place(relx=0.4, rely=0.05, relwidth=0.1)
        # k elementos tomados
        self.k1 = IntVar()
        self.lb_k1 = Label(self.cob, text="K", bg='#dfe3ee', fg='#107db2')
        self.lb_k1.place(relx=0.3, rely=0.25)
        self.k1_entry = Entry(self.cob, textvariable=self.k1)
        self.k1_entry.place(relx=0.4, rely=0.25, relwidth=0.1)
        self.bt_calcular2 = Button(self.cob, text="Calcular", bd=2,
                                   bg='#107db2', fg='white',
                                   font=('verdana', 8, 'bold'),
                                   command=self.butaoclickcob)
        self.bt_calcular2.place(relx=0.6, rely=0.15, relwidth=0.2,
                                relheight=0.25)
        # Resultado
        self.resultado1 = StringVar()
        self.resultado3 = Label(self.cob, textvariable=self.resultado1)
        self.resultado3.place(relx=0.4, rely=0.6, relwidth=0.1)
    def butaoclickarr(self):
        an = self.n.get()
        ak = self.k.get()
        n = an
        k = ak
        factorialn = 1
        factortiald =1
        d = n - k
        while an != 0:
            mutiplicaca = factorialn * an
            factorialn = mutiplicaca
            an = an - 1
        while d != 0:
            mutiplicacad = factortiald * d
            factortiald = mutiplicacad
            d = d - 1
        arranjo = factorialn/factortiald
        return self.resultado.set(arranjo)
    def butaoclickcob(self):
        an = self.n1.get()
        ak = self.k1.get()
        n = an
        k = ak
        factorialn = 1
        factortiald = 1
        factortialk = 1
        d = n - k
        while ak != 0:
            mutiplicaca = factortialk * ak
            factortialk = mutiplicaca
            ak = ak - 1
        while an != 0:
            mutiplicaca = factorialn * an
            factorialn = mutiplicaca
            an = an - 1
        while d != 0:
            mutiplicacad = factortiald * d
            factortiald = mutiplicacad
            d = d - 1
        f = factortiald*factortialk
        cob = factorialn/f
        return self.resultado1.set(cob)
    def Quit(self):
        self.root.destroy()
    def Menus(self):
        menubar = Menu(self.root)
        self.root.config(menu=menubar)
        filemenu = Menu(menubar)
        menubar.add_cascade(label="Opções", menu=filemenu)
        filemenu.add_command(label="Sair", command=self.Quit)
app()