finally got the execution flow right. The root app instantiates and gridss the input and look up frame => the input frame waits for input => the root app displays the data put in. I probably can still subclass the root app lookup() function, I just need to follow this execution flow. Happy! :D

tkinter-enter-classed-2.py

@@ -1,6 +1,5 @@
 import tkinter as tk
 from tkinter import ttk
-
 from generic import sanitize, type_hosts_listed, type_hosts_organized
 
 class App(tk.Tk):
@@ -12,21 +11,32 @@ class App(tk.Tk):
         container.pack(side="top", fill="both", expand=True)
 
         container.grid_rowconfigure(0, weight=1)
-        container.grid_columnconfigure(0, weight=1)
+        container.grid_rowconfigure(1, weight=1)
+        container.grid_columnconfigure(1, weight=1)
+        container.grid_columnconfigure(2, weight=1)
+        container.grid_columnconfigure(3, weight=1)
         self.var = tk.Variable()
+        self.blahblah = 315
+
+        input_frame = InputFrame(container, self)
+        input_frame.grid(row=0, column=0, sticky='nsew')
+        lookup_frame = LookupFrame(container, self)
+        lookup_frame.grid(row=1, column=0, sticky='nsew')
+        # self.lookup()
+
+    def lookup(self):
+        print("FROM THE APP CLASS")
+        print(self.var.get())
 
-        # I think this goes wrong for my purposes: I'm not switching frames in place, but keeping them besides each other. Find a simpler setup maybe?
-        self.frames = {}
-        for F in (InputFrame, LookupFrame):
-            frame = F(container, self)
-            frame.grid(row=0, column=0, sticky='nsew')
 
 class InputFrame(tk.Frame):
     def __init__(self, parent, controller):
         tk.Frame.__init__(self, parent)
+
+        self.controller = controller
+
         label = tk.Label(self, text="Input URL, IP, email address")
         label.pack(padx=10, pady=10)
-        self.var = tk.Variable()
     
         self.entry = ttk.Entry(self)
         self.entry.focus()
@@ -34,18 +44,33 @@ class InputFrame(tk.Frame):
         self.entry.bind("<Return>", self.key_handler_function)
 
     def key_handler_function(self, event) -> None:
-        inputs = self.entry.get()
-        sanitized = sanitize.strip_and_list(inputs)
-        typed = type_hosts_organized.type_hosts(sanitized)
-        self.var.set(typed)
+        self.event = event
+        self.inputs = self.entry.get()
+        self.sanitized = sanitize.strip_and_list(self.inputs)
+        self.typed = type_hosts_organized.type_hosts(self.sanitized)
+        print(self.controller.var.set(self.typed))
+        self.controller.lookup()
+
 
 class LookupFrame(tk.Frame):
     def __init__(self, parent, controller):
         tk.Frame.__init__(self, parent)
+        self.controller = controller
+        
+        self.var = controller.var.get()
+        
         label = tk.Label(self, text="Lookup information")
         label.pack(padx=10, pady=10)
-        var = controller.var.get()
-        print(var)
+
+        self.ip_listbox = tk.Listbox(self)
+        self.ip_listbox.pack(padx=10, pady=10)
+
+
+    def lookup(self):
+        whatever = self.controller.var.get()
+        print(whatever)
+
+
 
 if __name__ == "__main__":
     testObj = App()

tkinter-enter.py

@@ -79,6 +79,7 @@ url_listbox = tk.Listbox(root)
 email_label = tk.Label(root, text="email address => DMARC/SPF")
 email_listbox = tk.Listbox(root)
 var = tk.Variable()
+print(var)
 entrylabel.grid(column=1, row=0, columnspan=2, sticky="nsew")
 entry.grid(column=0, row=1, columnspan=4, sticky="nsew")
 ip_label.grid(column=0, row=2, columnspan=2, sticky="nsew")