あるサイトの変化を監視したいと思い作ってみました。現在は私の自己紹介文を監視していますがurlとclass_nameを変更すると他サイトでも使えます。
20秒毎にページデータを取得し、前回の取得時とデータが異なるかを表示しています。

import requests
import time

from bs4 import BeautifulSoup


url = "https://qiita.com/sssssssiiiiinnn"
class_name ='div.newUserPageProfile_info_body.newUserPageProfile_description'
file = "elems_text.txt"


def is_not_changed(old_elem, new_elem):
    return old_elem == new_elem


def set_old_elems():
    try:
        f = open(file)
        old_elems = f.read()
        print(f'{"old_elem":10} : {old_elems}')
    except:
        old_elems = ''
    return old_elems


def set_new_elems():
    response = requests.get(url)
    response.encoding = response.apparent_encoding
    bs = BeautifulSoup(response.text, 'html.parser')
    new_elems = str(bs.select(class_name))
    print(f'{"new_elem":10} : {new_elems}')
    return new_elems


def display_result(old_elem, new_elem):
    if not is_not_changed(old_elems, new_elems):
        f = open(file, 'w')
        f.writelines(new_elems)
        f.close()
        print("Change is detected!!")
    else:
        print("not changed...")


if __name__ == '__main__':
    try:
        while(1):
            print("="*100)
            new_elems = set_new_elems()
            old_elems = set_old_elems()
            display_result(old_elems, new_elems)
            time.sleep(20)
    except KeyboardInterrupt:
        print("Interrupted by Ctrl + C")