How to store values from an Entry widget for loop in tkinter?

Put the Entry instances into a list.

from tkinter import Tk, Frame, Label, Entry, Buttonclass App(Frame):    def __init__(root, master):        Frame.__init__(root, master)        root.grid()        root.create_widgets()    def get_values(root):        return [float(entry.get()) for entry in root.entries]    def calc_CR(root):        answer = sum(root.get_values()) #Replace with your own calculations        root.answer.config(text=str(answer))    def create_widgets(root):        root.entries = []        for i in range(20):            label = Label(root, text=str(i))            label.grid(row=i, column=0)            entry = Entry(root, width=8)            entry.grid(row=i, column=1)            entry.insert(0, '0.00')            root.entries.append(entry)        root.calc_button = Button(root, text='Calculate C/R', command=root.calc_CR)        root.calc_button.grid(row=20, column=0)        root.answer = Label(root, text='0')        root.answer.grid(row=20, column=1)    def run(root):        root.mainloop()root = Tk()root.title('C/R Calculator')app = App(root)app.run()