Python Combbox下拉列表框搜索

Question

我创建了一个Combobox GUI，允许用户通过在键盘上输入字母来搜索Combobox。

例如，如果用户输入字母“L”，它将在Combobox下拉列表中搜索以字母“L”开头的单词的第一次出现。

我只能在下拉列表关闭时搜索Combobox。下拉列表打开时是否可以搜索Combobox？这是我的代码。

import tkinter as tk

from tkinter import StringVar, Label, Button
from tkinter import font
from tkinter.ttk import Combobox

from string import ascii_uppercase


class Parking_Gui(tk.Frame):

    PARKING_LOTS = ('ARTX', 'BURG', 'CLAY_HALL', 'GLAB', 'HAMH_HUTC',
                    'HHPA', 'JVIC', 'LIBR', 'PLSU', 'POST', 'PROF',
                    'STEC', 'STRO_NORTH', 'STRO_WEST', 'TROP')  

    def __init__(self):
        """Sets up the window and widgets"""
        tk.Frame.__init__(self)

        self.myfont = font.Font(family="Calibri", size=11, weight="normal")

        self.master.geometry("315x125")
        self.master.title("MSU PARKING APP")
        self.master.rowconfigure(0, weight = 1)
        self.master.columnconfigure(0, weight = 1)
        self.grid(sticky = 'NW')

        # Label for the parking lots
        self.LotLabel = tk.Label(self, text = "MSU Parking", font=self.myfont)
        self.LotLabel.grid(row = 0, column = 0)

        # Combobox for parking lots
        self._ComboValue = tk.StringVar()
        self._LotCombo = Combobox(self, textvariable=self._ComboValue,
                                  state='readonly', height = '6',
                                  justify = 'center', font=self.myfont)

        # List of parking lots loaded into Combobox
        self._LotCombo['values']= Parking_Gui.PARKING_LOTS
        self._LotCombo.grid(row = 0, column = 1)


        # Button to open parking diagram
        self._button = tk.Button(self, text = "Open", font=self.myfont)
        self._button.bind('<Button-1>', self._runParkingLot)
        self._button.grid(row = 0, column = 2)

        # Press enter to open selected parking diagram
        self._LotCombo.bind("<Return>", self._runParkingLot)

        # Search Combobox values with keyboard
        self._LotCombo.bind("<Key>", self.findInBox)

        self._LotCombo.focus()

    def _runParkingLot(self, event):
        """Event handler for the button. Will run the
           functinon associated with selected item"""

        parkingLot = self._LotCombo.get()

        """The 'globals' keyword, will return a dictionary of every function,
           variable, etc. currently defined within the global scope."""
        if parkingLot in globals():
            func = globals()[parkingLot]
            func()

    def findInBox(self, event):
        """findInBox method allows user to search through PARKING_LOTS
           list values by keyboard press"""

        keypress = event.char.upper()

        # If user key press is in the alphabet
        if keypress in ascii_uppercase:
            for index, lot_name in enumerate(Parking_Gui.PARKING_LOTS):
                if lot_name.startswith(keypress):
                    self._LotCombo.current(index)
                    break

def main():
    Parking_Gui().mainloop()

main()