尝试将输入从下拉菜单返回到Tkinter中的变量

Question

I'm writing one of my first programs, and I can't figure out how to fix this issue. I started learning Python like a week ago and am still very new to Tkinter and OOP in general. I got this script (D&D NPC Generator) working without using OOP, but I wanted to see how to do it with OOP since that's how most people seem to prefer using Tkinter.

Here's the code for the Input window:

class Input:

    def __init__(self, master):

        ideals = ["Good", "Evil",
                  "Lawful", "Chaotic",
                  "Neutral", "Other"]

        ideal_selection = StringVar()
        ideal_selection.set(ideals[0])

        self.name_label = Label(master, text="NPC Name: ")
        self.name_entry = Entry(master)

        self.ideal_label = Label(master, text="Ideal Type: ")
        self.ideal_entry = OptionMenu(master, ideal_selection, *ideals)

        self.submit_button = Button(text="Submit", command=self.close_window)

        self.name_label.grid(row=0, column=0)
        self.name_entry.grid(row=0, column=1)

        self.ideal_label.grid(row=1, column=0)
        self.submit_button.grid(columnspan=2, row=3, column=0)

        self.ideal_entry.grid(row=1, column=1)

    def close_window(self):
        global name
        global ideal_type
        name = self.name_entry.get()
        ideal_type = self.ideal_selection.get()
        self.master.destroy()

And it's returning:

AttributeError: 'Input' object has no attribute 'ideal_selection'

I have no idea what's going wrong. My goal with this GUI window is to have the user type in a name for the NPC and then select an option from a drowbown menu for what kind of ideal the user wants the NPC to have. A fix and explanation of what I did wrong would be very helpful, thank you.

Answer 1

You've declared ideal_selection as a local variable and not a class instance variable. Therefore, calling self.ideal_selection.get() will fail as there is no self to reference.

You need to change the declaration from: ideal_selection = StringVar() to: this.ideal_selection = StringVar() and change all other references over to this.ideal_selection .

Note that you have done this for everything else ( self.name_entry ) ...

Afterword:

I'd like to discourage you from your use of global here. When you have tkinter running under OOP principles, you can return values from your class back to the calling script.

(Note also eventually I would recommend not using from tkinter import * ).

Have a look at what happens if your code is amended to:

#! /usr/bin/env python
# -*- coding: utf-8 -*-

import tkinter as tk
import sys

class Input(tk.Frame):

    def __init__(self, parent):

        tk.Frame.__init__(self, parent)
        self.parent = parent

        ideals = ["Good", "Evil",
                  "Lawful", "Chaotic",
                  "Neutral", "Other"]

        self.ideal_selection = tk.StringVar()
        self.ideal_selection.set(ideals[0])

        self.name_label = tk.Label(root, text="NPC Name: ")
        self.name_entry = tk.Entry(root)

        self.ideal_label = tk.Label(root, text="Ideal Type: ")
        self.ideal_entry = tk.OptionMenu(root, self.ideal_selection, *ideals)

        self.submit_button = tk.Button(text="Submit", command=self.close_window)

        self.name_label.grid(row=0, column=0)
        self.name_entry.grid(row=0, column=1)

        self.ideal_label.grid(row=1, column=0)
        self.submit_button.grid(columnspan=2, row=3, column=0)

        self.ideal_entry.grid(row=1, column=1)

    def close_window(self):
        #global name
        #global ideal_type
        self.name = self.name_entry.get()
        self.ideal_type = self.ideal_selection.get()
        #self.destroy()
        self.quit()

if __name__ == '__main__':
    root = tk.Tk()
    root.geometry("600x400+300+300")
    app = Input(root)
    root.mainloop()
    # Note the returned variables here
    # They must be assigned to external variables
    # for continued use
    returned_name = app.name
    returned_ideal = app.ideal_type
    print("Your name is: " + returned_name)
    print("Your ideal is: " + returned_ideal)
    # Should only need root.destroy() to close down tkinter
    # But need to handle user cancelling the form instead
    try:
        root.destroy()
    except:
        sys.exit(1)