Pin Pad in Klasse überführt

ui.py

@@ -10,7 +10,9 @@ from definitions import app_title, app_version
 
 # Pinpad
 
-def win_pinpad():
+class win_pinpad(tk.Toplevel):
+    def __init__(self, parent):
+        super().__init__(parent)
 
         def update_time():
             string_time = strftime('%A, der %d.%m.%Y - %H:%M:%S')
@@ -18,12 +20,10 @@ def win_pinpad():
             digital_clock.config(text=string_time)
             digital_clock.after(1000, update_time)
 
-    root = tk.Tk()
-    root.title(app_title + " " + app_version)
-    root.eval('tk::PlaceWindow . center')
+        self.title(app_title + " " + app_version)
 
         # Digital clock label configuration
-    digital_clock = tk.Label(root)
+        digital_clock = tk.Label(self)
         digital_clock.grid(row=0, column=0, columnspan=3, padx=10, pady=10)
         # Initial call to update_time function
         update_time()
@@ -37,10 +37,10 @@ def win_pinpad():
                 buttons["OK"].configure(state="disabled")
 
 
-    tk.Label(root, text="Benutzernummer:").grid(row=1, column=0)
+        tk.Label(self, text="Benutzernummer:").grid(row=1, column=0)
         UserNr = tk.StringVar()
         UserNr.trace("w", lambda name, index, mode, UserNr=UserNr: usernr_changed(UserNr))
-    usernr = tk.Entry(root, width=10, textvariable=UserNr)
+        usernr = tk.Entry(self, width=10, textvariable=UserNr)
         usernr.grid(row=1,column=1)
 
        # Pinpad
@@ -63,7 +63,7 @@ def win_pinpad():
         # Buttons definieren
         button_width = 7
         button_height = 3
-    pinframe = tk.Frame(root)
+        pinframe = tk.Frame(self)
         pinframe.grid(row=2, column=0, columnspan=3, padx=10, pady=10)
         buttons = { }
 
@@ -84,9 +84,25 @@ def win_pinpad():
 
         usernr.focus_set()
 
-    # Tkinter main loop
+class mainwindow(tk.Tk):
+    def __init__(self):
+        super().__init__()
 
-    root.mainloop()
+        self.geometry('300x200')
+        self.title('Main Window')
+
+        # place a button on the root window
+        tk.Button(self,
+                   text='Login Window',
+                   command=self.open_window).pack(expand=True)
+
+    def open_window(self):
+        window = win_pinpad(self)
+        window.grab_set()
+
+
+if __name__ == "__main__":
+    app = mainwindow()
+    app.mainloop()
 
-def win_userselection():