Python clock

[menator01]

I'm trying my luck with a clock
Just can't seem to get it to update.
I've tried with the both the after method and while loops.
It would appear that I'm not putting it in the right place in the code or I need to make a new function and call it.
Any help would be great. Thanks

# /usr/bin/env python3

import os
import tkinter as tk
from tkinter import ttk
from datetime import datetime



class AlarmClock:
    def __init__(self, master):
        self.master = master
        self.master.columnconfigure(0, weight=1)
        self.master.rowconfigure(0, weight=1)

        style = ttk.Style()
        style.configure('Clock.TFrame', background='slategray')
        self.clock_frame = ttk.Frame(self.master, style='Clock.TFrame', border=8)
        self.clock_frame.grid(column=0, row=0, sticky='new')
        self.clock_frame.grid_columnconfigure(0, weight=3)

        now = datetime.now()
        time_string = now.strftime('%H:%M:%S')
        self.show_time = tk.StringVar()
        self.show_time.set(time_string)
        self.clock()

    def clock(self):

        clock_nums = ttk.Style()
        clock_nums.configure('Clock.TLabel', background='black', foreground='red', anchor='n', \
                             font=('sans', 18, 'bold'), relief='ridge', padding=8)
        self.label = ttk.Label(self.clock_frame, text=self.show_time.get(), style='Clock.TLabel')
        self.label.grid(column=0, row=0, sticky='new')
        self.label.grid_columnconfigure(0, weight=3)




def main():
    root = tk.Tk()
    root.title('Alarm Clock')
    root.geometry('400x200+50+50')
    AlarmClock(root)
    root.mainloop()

if __name__ == '__main__':
    main()