[Tkinter] Unable to Access global Variable when switching between frames

[balenaucigasa]

from tkinter import *
import tkinter as tk
 
var = "0"
 
def changename(name): #function for changing global variable
    global var
    var = name
    print("your 'def changename' is: ", var)
    return var
 
class MiniProject(tk.Tk): #baseline code for adding/switching pages https://pythonprogramming.net/change-show-new-frame-tkinter/
    def __init__(self, *args, **kwargs): #takes in any argument /keyword arguments
        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.title("Main")
        self.frames = {}
         
        for F in (StartPage, PageM):
            frame = F(container, self)
            self.frames[F] = frame
            frame.grid(row=0, column=5, sticky="nsew")
             
        self.show_frame(StartPage)

         
    def show_frame(self, cont):
        frame = self.frames[cont]
        global var
        print("your 'def show_frame' is: ", var)
        #print(frame.__dict__)        #####
        #print(frame.__dict__.keys())
        #print(dir(frame._tclCommands))
        frame.tkraise()
     
 
class StartPage(tk.Frame): #Front page with buttons 1 to 5
    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        
        for x in [1,2,3,4,5]: #clicking button should bring me to PageOne with label as button number instead of "..."
            button = tk.Button(self, justify=CENTER, text=str(x), \
                               command= lambda j = x: [changename(name = j),controller.show_frame(PageM)]) #code that changes variable to button number
            button.pack(side = LEFT)
  


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

        var = IntVar()
        var.set(tk.Frame)
        label = tk.Label(self, textvariable=var) #Supposed to display button number
        label.pack(pady=10,padx=10)
        button1 = tk.Button(self, text="TO HOME", command= lambda: controller.show_frame(StartPage))
        button1.pack()

 
app = MiniProject(var)
app.mainloop()

StartPage is implemented incorrectly. You must have 5 classes for the 5 buttons created. Why? Each button creates a frame. 1 button = 1 frame = 1 class

You can find the original along with other suggestions here:

import tkinter as tk                # python 3
from tkinter import font  as tkfont # python 3
#import Tkinter as tk     # python 2
#import tkFont as tkfont  # python 2

class SampleApp(tk.Tk):

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

        self.title_font = tkfont.Font(family='Helvetica', size=18, weight="bold", slant="italic")

        # the container is where we'll stack a bunch of frames
        # on top of each other, then the one we want visible
        # will be raised above the others
        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 = {}
        for F in (StartPage, PageOne, PageTwo):
            page_name = F.__name__
            frame = F(parent=container, controller=self)
            self.frames[page_name] = frame

            # put all of the pages in the same location;
            # the one on the top of the stacking order
            # will be the one that is visible.
            frame.grid(row=0, column=0, sticky="nsew")

        self.show_frame("StartPage")

    def show_frame(self, page_name):
        '''Show a frame for the given page name'''
        frame = self.frames[page_name]
        frame.tkraise()


class StartPage(tk.Frame):

    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        self.controller = controller
        label = tk.Label(self, text="This is the start page", font=controller.title_font)
        label.pack(side="top", fill="x", pady=10)

        button1 = tk.Button(self, text="Go to Page One",
                            command=lambda: controller.show_frame("PageOne"))
        button2 = tk.Button(self, text="Go to Page Two",
                            command=lambda: controller.show_frame("PageTwo"))
        button1.pack()
        button2.pack()


class PageOne(tk.Frame):

    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        self.controller = controller
        label = tk.Label(self, text="This is page 1", font=controller.title_font)
        label.pack(side="top", fill="x", pady=10)
        button = tk.Button(self, text="Go to the start page",
                           command=lambda: controller.show_frame("StartPage"))
        button.pack()


class PageTwo(tk.Frame):

    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        self.controller = controller
        label = tk.Label(self, text="This is page 2", font=controller.title_font)
        label.pack(side="top", fill="x", pady=10)
        button = tk.Button(self, text="Go to the start page",
                           command=lambda: controller.show_frame("StartPage"))
        button.pack()


if __name__ == "__main__":
    app = SampleApp()
    app.mainloop()