tkinter Entry小部件中的可见文本变量

我在使用tkinter中的Entry box小部件时遇到了麻烦 . 我想在用户选择编辑 - > Backbone ...时打开一个新窗口 . 在这个窗口中，将显示许多Entry小部件（为简单起见，只有一个编码用于下面），它们显示存储在各种实例中的默认字符串Element . 用户应该能够编辑此字符串并通过单击“确定”将其保存并通过单击“默认”将其恢复为默认值 . 每次重新打开主干编辑器时，输入框应始终显示变量的当前值（如果重新启动整个程序，则不需要记住用户输入） .

打开“Backbone Editor”窗口后，Entry框应显示字符串文本变量，但我无法显示 .

from tkinter import *
from tkinter import ttk

class View(ttk.Frame):
    """Main GUI class"""

    def __init__(self, master = None):

        self.WIDTH = 450
        self.HEIGHT = 500

        self.lib = MolecularLibrary()

        # Set up the main window
        ttk.Frame.__init__(self, master, borderwidth=5, width=self.WIDTH, height=self.WIDTH)
        self.master.resizable(FALSE, FALSE)
        self.grid(column=0, row=0, sticky=(N, S, E, W))
        self.columnconfigure(0, weight=1)

        self.create_menus()

    def create_menus(self):
        """Produces the menu layout for the main window"""

        self.master.option_add('*tearOff', FALSE)

        self.menubar = Menu(self.master)
        self.master['menu'] = self.menubar

        # Menu Variables
        menu_edit = Menu(self.menubar)

        # Add the menus to the menubar and assign their variables
        self.menubar.add_cascade(menu=menu_edit, label = "Edit")

        ### Edit ###
        menu_edit.add_command(label="Backbone...", command=lambda : self.edit_backbone())


    def edit_backbone(self):
        """Shows a window where the backbone constituents can be edited"""
        backbone_window = Toplevel(borderwidth = 5)
        backbone_window.title("Backbone Editor")
        backbone_window.resizable(FALSE, FALSE)

        print("sugar value", self.lib.sugar_var)

        # LABELS FOR BACKBONE #
        # Phosphate annotations and input
        sugar_label = ttk.Label(backbone_window, text = "Sugar")

        #inputs
        sugar = ttk.Entry(backbone_window, textvariable = self.lib.sugar_var, justify = 'center', width=10)

        ### Buttons ###
        default = ttk.Button(backbone_window, text = "Defaults", command=lambda : defaults())
        okay = ttk.Button(backbone_window, text = "Okay", command=lambda : okay())
        cancel = ttk.Button(backbone_window, text = "Cancel", command=lambda : backbone_window.destroy())

        #content.grid(column=0, row=0)
        sugar_label.grid(column=2, row=1)
        sugar.grid(column=1, row=2, columnspan=3)

        default.grid(column=0, row=12, columnspan=3, pady=2)
        okay.grid(column=6, row=12, columnspan=3, pady=2)
        cancel.grid(column=9, row=12, columnspan=4, pady=2)

        backbone_window.focus()

        def defaults():
            """Reset the backbone and bases to their defaults."""

            self.lib.set_molecules()


        def okay():
            """Set the backbone and base variables to the user set values."""

            self.lib.sugar_var.new_formula(sugar.get())

            backbone_window.destroy()


class MolecularLibrary:
    """
    """

    def __init__(self, atom_file = r'C:\MyPyProgs\OSeq\resources\ATOMS.txt',
                 precision = 4):

        self.molecules = {}
        self.atom_file = atom_file
#         self.molecule_file = molecule_file

        # Variables
        self.set_molecules()


    def set_molecules(self):
        """
        Set all of the molecules for the backbone and bases to their default values and forumlae.
        """
                ### Sugar ###
        self.sugar_var = Element('C5H8O3', 'A')


    def add_molecule(self, molecule):
        """(MolecularLibrary, list) -> None
           Returns a dictionary of the molecule name as an Element
           {molecule[0]: Element}
        """
        print(molecule)
        tmp = self.get_mass(molecule[1])
        return {molecule[0]: Element(molecule[1], molecule[0], tmp[0], tmp[0])}

class Element:
    """
    Creates an element with the following construct:
    [symbol, name, monoisotopic, average]
    """

    def __init__(self, symbol, name):

        self.symbol = symbol
        self.name = name

    def __str__(self):

        return str([self.symbol, self.name])

    def get_name(self):
        """Returns the name of the Element"""

        return self.name

    def get_symbol(self):
        """Returns the symbol of the Element"""

        return self.symbol

    def new_formula(self, new_formula):
        """replace the formula with new_formaula and recalculate the 
           average and monoisotopic masses."""

        self.symbol = new_formula


if __name__ == "__main__":
    root = Tk()
    root.title("Sequencer")
    view = View(root)
    root.mainloop()

上面的代码是我程序的严重剥离版本，但具有相同的基本架构 . 我担心还有很多代码，我通常会尝试将其删除更多，但我不确定我遇到的问题是否来自架构 .