How to display variable value in tkinter-label

Question

This is my first foray into tkinter. I used an object-oriented approach for my application, but cannot get variable values displayed in tkinter labels. I am using python 3.7.1.

I have tried many suggestions from other posts, such as converting my strings to tkinter's StringVar() and displaying those, both with 'text=...' and 'textvariable=...' but so far everything has proven to be unfruitful.

import tkinter as tk

class NPCApp(tk.Tk):

    def __init__(self, *args, **kwargs):

        tk.Tk.__init__(self, *args, **kwargs)

        container = tk.Frame(self)
        container.pack(side="top", fill="both", expand=True)
        container.grid_rowconfigure(0, weight=1)
        container.grid_columnconfigure(0, weight=1)

        self.frames = {}
        self.profession = None

        for F in (StartPage, PageOne):
            frame = F(container, self)
            self.frames[F] = frame
            frame.grid(row=0, column=0, stick="nsew")

        self.show_frame(StartPage)


    def show_frame(self, cont):
        frame = self.frames[cont]
        frame.tkraise()

    def setProfession(self, given_profession):
        self.profession = given_profession

    def getProfession(self):
        return self.profession


class StartPage(tk.Frame):

    def __init__(self, parent, controller):

        tk.Frame.__init__(self, parent)
        tk.Label(self, text="Choose a profession for your NPC:").pack(pady=10, padx=10)

        tk.Radiobutton(self, text="Herbalist/Alchemist", variable=controller.profession, value="Herbalist", command=lambda: controller.setProfession("Herbalist")).pack()
        tk.Radiobutton(self, text="Blacksmith", variable=controller.profession, value="Smith", command=lambda: controller.setProfession("Smith")).pack()
        tk.Radiobutton(self, text="Shopkeeper", variable=controller.profession, value="Shopkeep", command=lambda: controller.setProfession("Shopkeep")).pack()
        tk.Radiobutton(self, text="Innkeep", variable=controller.profession, value="Innkeep", command=lambda: controller.setProfession("Innkeep")).pack()
        tk.Radiobutton(self, text="Officer of the city watch", variable=controller.profession, value="Officer", command=lambda: controller.setProfession("Officer")).pack()
        tk.Radiobutton(self, text="Member of the city watch", variable=controller.profession, value="Soldier", command=lambda: controller.setProfession("Soldier")).pack()
        tk.Radiobutton(self, text="Member of a council of elders", variable=controller.profession, value="Councilmember", command=lambda: controller.setProfession("Councilmember")).pack()
        tk.Radiobutton(self, text="Regular citizen", variable=controller.profession, value="Citizen", command=lambda: controller.setProfession("Citizen")).pack()
        tk.Radiobutton(self, text="Foreign human", variable=controller.profession, value="Foreigner", command=lambda: controller.setProfession("Foreigner")).pack()

        tk.Button(self, text="To Page One",
                            command=lambda: controller.show_frame(PageOne)).pack()


class PageOne(tk.Frame):

    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)

        tk.Label(self, text=controller.getProfession()).pack(pady=10, padx=10)

        tk.Button(self, text="Back to Home",
                            command=lambda: controller.show_frame(StartPage)).pack()


app = NPCApp()
app.mainloop()

What you can see here is my application. You use the Radiobuttons to choose from a selection of NPC professions and the corresponding value is set internally, which is tested and works fine. However, displaying said value on PageOne in the label does not work. The page shows a blank followed by the 'Back to Home'-button, but should show the chosen profession and then said button beneath it.

Help me Stack Overflow, you are my only hope.

Answer 1

I suggest you make the getProfession return a StringVar and change setProfession to set that StringVar (create it in the __init__. Then you can create your tk.Label with textvariable=controller.getProfession() and the label text will be updated from the StringVar whenever you call setProfession.

class NCApp(tk.Tk):
    def __init__(...):
        self.profession = tk.StringVar()
        ...
    def setProfession(self, given_profession):
        self.profession.set(given_profession)
    def getProfession(self):
        return self.profession

class PageOne(tk.Frame):
    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        self.label = tk.Label(self, textvariable=controller.getProfession())
        self.label.pack(pady=10, padx=10)
        ...