I'm learning tkinter off of the Sentdex tutorials and I into a problem when trying to change pages. My compiler throws something about a KeyError that it doesn't give whenever I change the button on the start page to change to itself rather than PageOne:

Exception in Tkinter callback
Traceback (most recent call last):File "C:\Users\Jason\AppData\Local\Programs\Python\Python35-32\lib\tkinter\__init__.py", line 1549, in __call__return self.func(*args)File "C:/Users/Jason/PycharmProjects/gui/main.py", line 43, in <lambda>button1 = tk.Button(self, text="Visit Page 1",command=lambda: controller.show_frame(PageOne))File "C:/Users/Jason/PycharmProjects/gui/main.py", line 29, in show_frameframe = self.frames[cont]
KeyError: <class '__main__.PageOne'>

and my code:

import tkinter as tkLARGE_FONT=("Verdana", 12)class SeaofBTCapp(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 = {}frame = StartPage(container, self)self.frames[StartPage] = frameframe.grid(row=0, column=0, sticky="nsew")self.show_frame(StartPage)def show_frame(self, cont):frame = self.frames[cont]frame.tkraise()def qf(param):print(param)class StartPage(tk.Frame):def __init__(self, parent, controller):tk.Frame.__init__(self, parent)label = tk.Label(self, text="Start Page", font=LARGE_FONT)label.pack(pady=10,padx=10)#command within button cant throw args to funcs. Use lambda to throw those args to the func insteadbutton1 = tk.Button(self, text="Visit Page 1",command=lambda: controller.show_frame(PageOne))button1.pack()class PageOne(tk.Frame):def __init__(self, parent, controller):tk.Frame.__init__(self, parent)label = tk.Label(self, text="Start Page", font=LARGE_FONT)label.pack(pady=10,padx=10)#command within button cant throw args to funcs. Use lambda to throw those args to the func insteadbutton1 = tk.Button(self, text="Visit Page 1",command=lambda: controller.show_frame(StartPage))button1.pack()app = SeaofBTCapp()
app.mainloop()

Your button is calling show_frame(PageOne), but you never created an instance of PageOne. So, of course, there is no key in self.frames that matches that page.

Perhaps you intended to create an instance of PageOne in your initial code?

def __init__(self, *args, **kwargs):...frame = PageOne(container, self)self.frames[PageOne] = frame...

If you don't want to create the page until you need it, you can add that code in show_frame. First, you'll need to make container an instance variable (ie: self.container), then modify show_frame to look something like this:

def show_frame(self, cont):if cont not in self.frames:self.frames[cont] = cont(self.container, self)frame = self.frames[cont]frame.tkraise()