A script to detect price drop

price_watcher.py

#!/usr/bin/python3

# This script is supposed to be run on a linux machine with a mail server, i.e. can send emails via the `mail` command.
# Can use cron to set up a schedule to run the script.

import re
import requests
import subprocess
import time

# If items are too many, can store them in a csv or json and read it here.
items = [
        ('https://xxxxx', 0)  # replace with tuples of (product URL, price)
        ]

mail_user = ''        # replace with mail user name
log_file = 'log.txt'  # replace with local log file name

# If items are from multiple websites, can add the regex into the item list.
# If all items come from the same website, can use a pair of global variables as below.
regex_price = '"price":"([0-9\.]+)"'  # replace with regex to match the price, different for each website
regex_name = '/([a-z\-]+)$'           # replace with regex to match the product name in the URL, different for each website


f = open(log_file, 'a')

for (item, price) in items:
    r = requests.get(item)
    m = re.search(regex_price, r.text)
    if m:
        p = float(m.group(1))
        if p < price:
            n = re.search(regex_name, item)
            if n:
                name = n.group(1)
                email_subject = "Price drop detected: "+name
                email_content = "original price: "+str(price)+"\ncurrent price: "+str(p)+"\n"+item+"\n"
                email_process = subprocess.Popen(["mail", "-s", email_subject, mail_user], stdin=subprocess.PIPE)
                email_process.stdin.write(email_content.encode())
                email_process.stdin.close()
                if f:
                    f.write("\n["+time.ctime()+"] email sent for "+name+" "+str(price))
                  
if f:
    f.write("\n["+time.ctime()+"] scan completed")
    f.close()