This example code is for Raspberry Pi Selfie Tutorial.

selfie.py

import RPi.GPIO as GPIO
from picamera import PiCamera
import time
from time import sleep

camera = PiCamera()
Button = 20
Buzzer = 26

GPIO.setwarnings(False)  
GPIO.setmode(GPIO.BCM)
GPIO.setup(Button, GPIO.IN, GPIO.PUD_UP)
GPIO.setup(Buzzer,GPIO.OUT)

def beep(times, sec):
  for x in range(times):
    GPIO.output(Buzzer,GPIO.HIGH)
    sleep(sec)
    GPIO.output(Buzzer,GPIO.LOW) 
    sleep(sec)

try: 
    while True:
        if GPIO.input(Button) == 0:
            beep(2, 0.07)
            filename = (time.strftime("%y%b%d_%H:%M"))
            camera.rotation = 180
            camera.start_preview(fullscreen=False, window = (600, 10, 640, 480))
            sleep(3)
            beep(1, 0.5)
            variable = "/home/pi/Desktop/" + filename + ".jpg"
            camera.capture(variable)
            #camera.capture("/home/pi/Desktop/{0}".format(Filename))
            camera.stop_preview()

        else :
          GPIO.output(Buzzer,GPIO.LOW)  

except KeyboardInterrupt:
    GPIO.cleanup()