单击重置按钮(重置在选项菜单上所做的选择)后，选项菜单对其他选项菜单的依赖不起作用

Question

我正在尝试创建一个UNIT CONVERTER，它是一个使用Tkinter的Python GUI应用程序。我已经创建了一个主选项菜单和两个其他选项菜单。其他两个选项菜单依赖于主选项菜单，即从主选项菜单中选择一个值后，其他两个可选菜单中的值列表会发生变化。我已经创建了两个按钮"；转换"；以及"；重置"；。在重置按钮中，我试图重置所有三个选项菜单上的选择

源代码

import tkinter as tk
from tkinter import messagebox
from math import * 

root = tk.Tk()
root.title("Unit Converter")
root.geometry("600x400")
# A function for updating the dropdown lists upon selecting the operation.
def updateSubLists(self):
y.set('')
z.set('')
subUnitListFrom['menu'].delete(0,'end')
subUnitListTo['menu'].delete(0,'end')

for item in list(listOfUnits.get(x.get())):
subUnitListFrom['menu'].add_command(label=item,command=tk._setit(y,item))
subUnitListTo['menu'].add_command(label=item,command=tk._setit(z,item))

y.set(list(listOfUnits.get(x.get()))[0])
z.set(list(listOfUnits.get(x.get()))[0])
# A callback function to validate if the data entered is only digit or not.
def validateUserInput(input):
"""This method validates the data entered by the User to check if the entered data is a number or not."""
if input.isdigit() == True:
return True
elif input == "":
return True
else:
messagebox.showinfo("Information","Only number is allowed")
return False

# A function for resetting the entries selected.
def resetEntries():
""" This method helps in resetting the entries given as a input or selected by the User"""
x.set("")
unitList["menu"].delete(0,'end')
for item in list(listOfUnits.keys()):
unitList['menu'].add_command(label=item,command=tk._setit(x,item))
x.set(list(listOfUnits.keys())[0])

#updateSubLists('')
y.set('')
z.set('')
subUnitListFrom['menu'].delete(0,'end')
subUnitListTo['menu'].delete(0,'end')

for item in list(listOfUnits.get(x.get())):
subUnitListFrom['menu'].add_command(label=item,command=tk._setit(y,item))
subUnitListTo['menu'].add_command(label=item,command=tk._setit(z,item))

y.set(list(listOfUnits.get(x.get()))[0])
z.set(list(listOfUnits.get(x.get()))[0])

# Lists and Sub-lists creation 
#listOfUnits = ['Area','Energy','Frequency','Length','Mass','Pressure','Speed','Temperature',
#'Time','Volume']
listOfUnits = {"Area":['Square Kilometer','Squatre Meter','Square Mile','Square Yard','Square Foot','Square Inch','Hectare','Acre'],
"Energy":['Joule','Kilo Joule','Gram Calorie','Kilo Calorie'],
"Frequency":['Hertz','Kilohertz','Megahertz','Kilohertz'],
"Length":['Kilometer','Meter','Centimeter','Millimeter','Micrometer','Nanometer','Mile','Yard','Foot','Inch'],
"Mass":['Tonne','Kilogram','Microgram','Milligram','Gram','Pound','Ounce'],
"Pressure":['Bar','Pascal','Pound per square inch','Standard atmosphere','Torr'],
"Speed":['Miles per hour','Meter per second','Foot per second','Kilometer per hour','Knot'],
"Temperature":['Celcius','Farhenheit','Kelvin'],
"Time":['Nanosecond','Microsecond','Millisecond','Second','Minute','Hour','Day','Week','Month','Calender Year','Decade','Century'],
"Volume":['Litre','Millilitre','Imperial Gallon','Imperial Pint']
}
# label text for header title
headerLbl = tk.Label(root,text="UNIT CONVERTER",fg="black",bg="light grey",font = ("Times New Roman", 30,"bold","italic","underline"))
headerLbl.grid(row = 0,column = 1,columnspan = 3)
# Label text for conversion tye selection 
lbl1 = tk.Label(root,text="Type of Conversion:")
lbl1.grid(row = 1,column = 0,padx=20,pady=20)

# OptionMenu creation for the list of Units to select
global x 
x = tk.StringVar()
x.set(list(listOfUnits.keys())[0])
unitList = tk.OptionMenu(root,x,*listOfUnits.keys(),command=updateSubLists)
unitList.grid(row = 1,column = 1,padx=20,pady=40)
# Label text for conversion type selection 
lbl2 = tk.Label(root,text="From")
lbl2.grid(row = 2,column = 0)

# OptionMenu creation for the list of Sub Units to select.
global y 
y = tk.StringVar()
y.set(list(listOfUnits.get(x.get()))[0])
subUnitListFrom = tk.OptionMenu(root,y,*listOfUnits.get(x.get()))
subUnitListFrom.grid(row=2,column=1,padx=20,pady=40)

# Entry widget for From label
fromEntry = tk.Entry(root,width=20)
valid_info = root.register(validateUserInput)   # register the function for the validation
fromEntry.config(validate="key",validatecommand=(valid_info,'%P'))  # Adding the properties for validation elements
fromEntry.grid(row=2,column=2)
# Label text for conversion type selection 
lbl3 = tk.Label(root,text="To")
lbl3.grid(row = 3,column = 0)
# OptionMenu creation for the list of Sub Units to select.
global z 
z = tk.StringVar()
z.set(list(listOfUnits.get(x.get()))[0])
subUnitListTo = tk.OptionMenu(root,z,*listOfUnits.get(x.get()))
subUnitListTo.grid(row=3,column=1)
# Entry widget for From label
ToEntry = tk.Entry(root,width=20,state="readonly")
ToEntry.grid(row=3,column=2)
# Logic for the convert button
convert_button = tk.Button(root,text="CONVERT",fg="black",bg ="yellow",font=("Times New Roman",12,"bold"))
convert_button.grid(row=4,column=1,padx=20,pady=40)
# Logic for the reset button
reset_button = tk.Button(root,text="RESET",fg="black",bg="yellow",font=("Times New Roman",12,"bold"),command=resetEntries)
reset_button.grid(row=4,column=2,padx=20,pady=40)
root.mainloop()

问题陈述：单击"重置"时，逻辑工作成功，但当我再次在主OptionMenu中选择新值时，相应的值列表不会反映在其他两个OptionMenu中。我不能理解"；在我点击重置按钮后，为什么当我更改主选项菜单的值时，我的其他两个下拉菜单没有反映相应的值；。

Answer 1

您忘记在resetEntries():中传递updateSubLists作为tk._setit(...)的第三个参数

def resetEntries():
""" This method helps in resetting the entries given as a input or selected by the User"""
x.set("")
unitList["menu"].delete(0,'end')
for item in list(listOfUnits.keys()):
unitList['menu'].add_command(label=item,command=tk._setit(x,item,updateSubLists))
...