Q:

Refresh a tkinter frame on button press

I am utilising code from Switch between two frames in tkinter to make my GUI.  I have a frame with refresh and restart buttons.
My original idea was for the restart button to go to the start page as in the code below but if this frame is called again it has the entries from the previous attempt still showing.
I've tried.destroy() for the refresh button but then I get an traceback message  when I call the PLG frame again.
For the restart button, how would I close the PLG frame, go to the Start page and then be able to select PLG again?
For the refresh button, how would I remove the entries in the entry widget and text arrear so that another entry can be made and new answer returned?
class PLG(tk.Frame):
    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        self.controller = controller
        label = tk.Label(self, text="Enter the engine size (cc) below", font=controller.title_font)
        label.pack(side="top", fill="x", pady=10)
        vcmd = (self.register(self.onValidate), '%S')
        self.weight_entry = tk.Entry(self, validate='key', vcmd = vcmd)
        self.weight_entry.pack(pady = 10)
        tk.Button(self, text='Click here to display price', command=self.show_option).pack()
        self.text = tk.Text(self)
        self.text.pack(pady = 10)
        self.text.config(state='disabled')
        restart_button = tk.Button(self, text="Restart",
              command=self.restart)
        restart_button.pack()
        refresh_button = tk.Button(self, text="Refresh", command=self.refresh).pack() 
        refresh_button.pack()  

    def onValidate(self,S):
    if S in ['0','1','2', '3', '4', '5', '6', '7', '8', '9']: 
        return True
    else:
        self.bell() # adds a sound effect to error
        self.text.delete(1.0, tk.END) # deletes the error message if valid entry provided
        self.text.insert(tk.END, "Invalid entry.  Please try again.") # displays an error message if a number not provided in entry widget
        return False

    def restart(self):
        self.refresh()
        show_frame("StartPage")

    def refresh(self):
        self.text.config(state='normal')
        self.weight_entry.delete(0,tk.END)
        self.text.delete("1.0", "end")

Advice on both elements would be appreciated.

A:

The first step is to have your button call a proper function rather than using lambda. Unless you understand why and when to use lambda, it usually just makes the code harder to write and understand.
Once you have it call a function, you can use the function to clear the entries.
Example:
class PLG(tk.Frame):
    def __init__(self, parent, controller):
        ...
        tk.Button(self, text="Restart", command=self.restart)
        tk.Button(self, text="Refresh", command=self.refresh)
        ...

    def restart(self):
        self.refresh()
        self.controller.show_frame("StartPage")

    def refresh(self):
        self.weight_entry.delete(0, "end")
        self.text.delete("1.0", "end")

