Python-Tkinter-如何从下拉选项中获取值并传递给另一个函数

Question

Please suggest how to use the selected drop down value in another function(sample()) in below code snippet.

I was able to create a two functions fun() and fun2() which returns the first dropdown value and second dropdown value, but i was unable to pass the selected dropdown value as a parameter.

import sys
import tkinter.messagebox as box
from tkinter.filedialog import asksaveasfile
if sys.version_info[0] >= 3:
    import tkinter as tk
else:
    import Tkinter as tk


class App(tk.Frame):

    def __init__(self, master):
        tk.Frame.__init__(self, master)

        self.dict = {'Asia': ['Japan', 'China', 'Malaysia'],
                     'Europe': ['Germany', 'France', 'Switzerland']}

        self.variable_a = tk.StringVar(self)
        self.variable_b = tk.StringVar(self)

        self.variable_b.trace('w', self.fun2)
        self.variable_a.trace('w', self.update_options)


        self.optionmenu_a = tk.OptionMenu(self, self.variable_a, *self.dict.keys(), command=self.fun)
        self.optionmenu_b = tk.OptionMenu(self, self.variable_b, '')


        username = self.fun()
        password = self.fun2()


        self.button = tk.Button(self, text="Login", command=lambda : sample(username=username, password=password))


        self.variable_a.set('Asia')

        self.optionmenu_a.pack()
        self.optionmenu_b.pack()
        self.button.pack()
        self.pack()

    def fun(self,*args):
        return self.variable_a.get()

    def fun2(self, *args):
        return self.variable_b.get()


    def update_options(self, *args):
        countries = self.dict[self.variable_a.get()]
        self.variable_b.set(countries[0])

        menu = self.optionmenu_b['menu']
        menu.delete(0, 'end')

        for country in countries:
            menu.add_command(label=country, command=lambda nation=country: self.variable_b.set(nation))


def sample(username, password):
    box.showinfo('info', 'Enter Credentials')


if __name__ == "__main__":
    root = tk.Tk()
    username = "root"
    password = "admin"
    app = App(root)
    app.mainloop()

Answer 1

Just before first dropdown call its command self.fun an self.variable_b.trace('w', self.fun2) is called, so dropdown 2 will change its value faster than 1 dropdown, that can be confirmed with print in fun/fun2:

def fun(self,*args):
    print("value 1dd: " + self.variable_a.get())
    return self.variable_a.get()

def fun2(self, *args):
    print("value 2dd: " + self.variable_b.get())
    return self.variable_b.get()

I would not use the optionmenu since it can't receive focus, you can use instead the combobox, also if the question is Please suggest how to use the selected drop down value in another function then look this example:

import sys
import tkinter.messagebox as box
from tkinter.filedialog import asksaveasfile
if sys.version_info[0] >= 3:
    import tkinter as tk
    import tkinter.ttk as ttk
else:
    import Tkinter as tk


class App(tk.Frame):

    def __init__(self, master):
        tk.Frame.__init__(self, master)

        self.dict = {'Asia': ['Japan', 'China', 'Malaysia'],
                     'Europe': ['Germany', 'France', 'Switzerland']}

        self.variable_a = tk.StringVar(self)
        self.variable_b = tk.StringVar(self)
        self.last_county = tk.StringVar(self)
        self.area = tk.StringVar(self)
        self.country = tk.StringVar(self)

        self.variable_b.trace('w', self.fun2)
        self.variable_a.trace('w', self.update_options)


        self.combobox_a = ttk.Combobox(self, values=list(self.dict.keys()), state='readonly')
        self.combobox_a.bind("<<ComboboxSelected>>", self.fun)
        self.combobox_a.current(0)
        self.combobox_b = ttk.Combobox(self, values=self.dict['Asia'], state='readonly')
        self.combobox_b.bind("<<ComboboxSelected>>", self.fun2)
        self.combobox_b.current(0)


        username = self.fun()
        password = self.fun2()


        self.button = tk.Button(self, text="Login", command=lambda : sample(username, password, self.area, self.country))


        # self.variable_a.set('Asia')

        self.combobox_a.pack()
        self.combobox_b.pack()
        self.button.pack()
        self.pack()

    def fun(self,*args):
        print("changed 1-st combobox value to: " + self.combobox_a.get())
        if self.last_county != self.combobox_a.get():
            self.combobox_b['values']=self.dict[self.combobox_a.get()]
            self.combobox_b.current(0)
        self.last_county = self.area = self.combobox_a.get()
        return self.variable_a.get()

    def fun2(self, *args):
        print("changed 2-nd combobox value to" + self.combobox_b.get())
        self.country = self.combobox_b.get()
        return self.variable_b.get()

    def update_options(self, *args):
        countries = self.dict[self.variable_a.get()]
        self.variable_b.set(countries[0])

        menu = self.combobox_b['menu']
        menu.delete(0, 'end')

        for country in countries:
            menu.add_command(label=country, command=lambda nation=country: self.variable_b.set(nation))


def sample(username, password, area, country):
    box.showinfo('info', 'Selected area: ' + area + '\nSelected country: ' + country + '\nEnter Credentials')

if __name__ == "__main__":
    root = tk.Tk()
    username = "root"
    password = "admin"
    app = App(root)
    app.mainloop()

I created two variables self.area and self.country which gets its values from fun() / fun2() functions, and showed how to use them in sample() function.

Update :

I don't know but i guessed that you are about to create something like this:

import sys
import tkinter.messagebox as box
from tkinter.filedialog import asksaveasfile
if sys.version_info[0] >= 3:
    import tkinter as tk
    import tkinter.ttk as ttk
else:
    import Tkinter as tk


class App(tk.Frame):

    def __init__(self, master):
        tk.Frame.__init__(self, master)
        self.dict = {'Asia': ['Japan', 'China', 'Malaysia'],
                     'Europe': ['Germany', 'France', 'Switzerland']}
        # Init labels
        self.label_a = tk.Label(self, text="User Name: ")
        self.label_b = tk.Label(self, text="Password: ")
        # Initialize entries
        self.entry_a = tk.Entry(self)
        self.entry_b = tk.Entry(self, show='*') # Make a password entry
        # Add clear on double-click
        self.entry_a.bind("<Double-1>", lambda cl: self.entry_a.delete(0, "end"))
        self.entry_b.bind("<Double-1>", lambda cl: self.entry_b.delete(0, "end"))
        # Set default text
        self.entry_a.insert("0", "BladeMight")
        self.entry_b.insert("0", "lalala7x256")
        # Initialize comboboxes
        self.combobox_a = ttk.Combobox(self, values=list(self.dict.keys()), state='readonly')
        self.combobox_b = ttk.Combobox(self, values=self.dict['Asia'], state='readonly')
        # Select 0 element
        self.combobox_a.current(0)
        self.combobox_b.current(0)
        # Add event to update variables on combobox's value change event
        self.combobox_a.bind("<<ComboboxSelected>>", lambda f1: self.fun())
        self.combobox_b.bind("<<ComboboxSelected>>", lambda f2: self.fun2())
        # Initialize variables
        self.area = self.combobox_a.get()
        self.last_area = self.country = self.combobox_b.get()
        self.username = self.password = tk.StringVar(self)
        # Intialize button with command to call sample with arguments
        self.button = tk.Button(self, text="Login", command=lambda: sample(self.area, self.country, self.entry_a.get(), self.entry_b.get()))
        # Place all controls to frame
        self.label_a.pack()
        self.entry_a.pack()
        self.label_b.pack()
        self.entry_b.pack()
        self.combobox_a.pack(pady=5)
        self.combobox_b.pack(pady=5)
        self.button.pack()
        self.pack()

    def fun(self):
        print("changed 1-st combobox value to: " + self.combobox_a.get())
        if self.last_area != self.combobox_a.get():
            self.combobox_b['values']=self.dict[self.combobox_a.get()]
            self.combobox_b.current(0)
            self.country = self.combobox_b.get()
        self.last_area = self.area = self.combobox_a.get()

    def fun2(self):
        print("changed 2-nd combobox value to: " + self.combobox_b.get())
        self.country = self.combobox_b.get()

def sample(area, country, username, password):
    box.showinfo('info', 'User Name: ' + username + '\nPassword: ' + password + '\n' + 'Selected area: ' + area + '\nSelected country: ' + country + '\n')

if __name__ == "__main__":
    root = tk.Tk()
    username = "root"
    password = "admin"
    app = App(root)
    app.mainloop()

right?