price-alert.py

#!/usr/bin/python
import time
import requests
import smtplib
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from lxml import html
import ConfigParser

config = ConfigParser.RawConfigParser()
config.read("creds")
email_user = config.get('email','user')
email_pass = config.get('email','pass')


# Change these values to your desired sale page (the selector and price check were tested on Amazon).
BASE_URL = "http://www.amazon.com/exec/obidos/ASIN/"
SMTP_URL = "smtp.gmail.com:587"
XPATH_SELECTOR = '//*[@id="priceblock_ourprice"]'
SLEEP_INTERVAL = 10
#ITEMS is a list of lists, storing ASINs and their maximum prices
ITEMS = [['B0042A8CW2',100]]

def send_email(price):
    global BASE_URL

    try:
        s = smtplib.SMTP(SMTP_URL)
        s.starttls()
        s.login(email_user, email_pass)
    except smtplib.SMTPAuthenticationError:
        print("Failed to login")
    else:
        print("Logged in! Composing message..")
        msg = MIMEMultipart("alternative")
        msg["Subject"] = "Price Alert - {}".format(price)
        msg["From"] = email_user
        msg["To"] = email_user
        text = "The price is currently {0} !! URL to salepage: {1}".format(price, BASE_URL)
        part = MIMEText(text, "plain")
        msg.attach(part)
        s.sendmail(email_user, email_user, msg.as_string())
        print("Message has been sent.")

while True:
    #item[0] is the item's ASIN while item[1] is that item's maximum price
	for item in ITEMS:
		r = requests.get(BASE_URL + item[0])
		tree = html.fromstring(r.text)
		try:
			#We have to strip the dollar sign off of the number to cast it to a float
			price = float(tree.xpath(XPATH_SELECTOR)[0].text[1:])
		except IndexError:
			print("Didn't find the 'price' element, trying again")
			continue
		if price <= item[1]:
			print("Price is {}!! Trying to send email.".format(price))
			send_email(price)
			break
		else:
			print("Price is {}. Ignoring...".format(price))

	print "Sleeping for {} seconds".format(SLEEP_INTERVAL)
	time.sleep(SLEEP_INTERVAL)